What is the biblical basis for the idea that God loves everyone equally? Equally meaning he doesn't love someone more or less than anyone else?
I am not aware of a verse that says explicitly that "God loves everyone equally". In fact, there are some verses to suggest that some are loved more than others, which is not your question so will be neglected1, but there are several that indicate that God indeed loves all people.
The first is probably the most quoted Bible verse of all time:
For God so loved the world, that He gave His only begotten Son, that whoever believes in Him shall not perish, but have eternal life.
John 3:16 (NASB)
That verse stresses that God loved the world, which colloquially means everyone. Additionally, the love is so great that the greatest gift of all, eternal life, is offered to everyone. Now there's not a direct statement of "love equality" in John 3, but there is a good case to be made that God loves everyone greatly.
This thought continues in Romans 5, 1 Timothy, and 2 Peter:
But God demonstrates His own love toward us, in that while we were yet sinners, Christ died for us.
Romans 5:8 (NASB)
[God] desires all men to be saved and to come to the knowledge of the truth.
1 Timothy 3:9 (NASB)
The Lord is not slow about His promise, as some count slowness, but is patient toward you, not wishing for any to perish but for all to come to repentance.
2 Peter 3:9 (NASB)
It seems odd to suggest that God does not love anybody in light of these verses, however, it does not mean there is "love equality", however, when the love of God was the motivation to offer all people eternal life, we are talking about a love in which the minimum level is exceedingly great.
The perspective given on GotQuestions.org makes a distinction between merciful love, which extends to everyone and keeps God from annihilating everyone at the moment of sin, and covenant love, which extends to only Christians and brings the gift of eternal life for the condition of accepting Jesus. I find that the view is common among Christians.
FIRST THINGS FIRST
I hate to sound like Pilate, but "What is love?"
A decent answer to your question depends first on an answer that question, particularly as it relates to God's love for us human critters.
We're all somewhat familiar with the "four loves": the love of friends (phileo), the love of family members (storge), the love of romance and marital love (eros), and godly love (agape).
Let's assume for the sake of argument that God loves people with strictly agape love, which in essence is an unselfish, sacrificial type of love by which God is not out to get something from us but to give something to us, regardless of who we are and what we can do for him. God obviously looks beyond our faults and failings and sees our deepest needs. He also desires to meet those needs.
"God demonstrates His own love toward us, in that while we were yet sinners, Christ died for us" (Romans 5:8 NASB Updated).
Dying love is of course the greatest expression of love. Jesus told us,
"Greater love hath no man than this, that a man lay down his life for his friends. Ye are my friends, if ye do the things which I command you" (John 15:13-14 KJV).
Jesus' words, above, preceded the apostle Paul's words in Romans 5:8. Put the two thoughts together, however, and you wind up with something like this:
Jesus told his disciples in effect that he was willing to lay down his life for them.
The very least they could do in appreciation for that kind of love is to obey him.
Calvary, of course, was yet future when he shared these words with his disciples (though he told them time and time again that his death was coming).
In Romans, Paul looks back on the death of Jesus as a fait accompli. He expands upon the idea of why and for whom Christ died:
The "good Samaritan" of Jesus' story (Luke 10:30 ff.) illustrates true love. In fact, Jesus was very much like that Samaritan in that his own people, the Jews, treated him like a hated outsider, just as they treated the hated Samaritans. John tells us
"He came to His own, and those who were His own did not receive Him" (John 1:11),
All this to say: God's love is like no other love. As the hymn writer expressed it:
The love of God is greater far
Than tongue or pen could ever tell.
It goes beyond the highest star
And reaches to the lowest hell . . .
Could we with ink the ocean fill,
And were the sky with parchment made,
Were every stalk on earth a quill
And every man a scribe by trade
To write the love of God above
Would drain the ocean dry,
Nor could the scroll contain the whole
Though stretched from sky to sky
GOD IS AN EQUAL OPPORTUNITY GOD
My answer thus far has simply laid the groundwork for the assertion that God's love for us is uniquely divine and has no earthly counterpart.
The second part to my answer touches on something which previous answerers have mentioned, and that is that God is not a respecter of persons.
And Peter opened his mouth and said, "Of a truth I perceive that God is no respecter of persons" (Acts 10:34 ASV).
Some other versions are worded slightly differently, and here are a few of them:
Peter said, "I really am learning that God doesn't show partiality to one group of people over another" (CEBA).
Then Kefa addressed them: "I now understand that God does not play favorites" (CJB).
Peter began to speak: "I now realize that it is true that God treats everyone on the same basis" (GNT).
So Peter opened [his] mouth [and] said, "In truth I understand that God is not one who shows partiality" (LEB).
Then Peter began to speak. "I now realize how true it is that God treats everyone the same" (NIRV).
Then Peter began to speak. "I clearly see," he said, "that God makes no distinctions between one man and another (WNT).
In context, Peter's realization came on the heels of his being summoned to the house of Cornelius, a Gentile, whom God sent a heavenly visitant. Cornelius, a resident of Caesarea, is described in this passage as a man who prayed to God and was a giver of alms. The visitant told Cornelius that God remembered his prayers and alms, and that he was to go ask the Jewish apostle Peter, who was in Joppa at the time (about 35 miles from Caesarea) to pay him a visit.
Although Peter was considered to be an "apostle to the Jews" (Galatians 2:8), when he arrived at Cornelius's house and was made aware that Cornelius was a "God fearer," he then realized that God was reaching out to Gentiles as well as Jews with the message of the Gospel of Jesus Christ.
The application to the question before us: In gathering a people to himself, God reaches beyond the narrow confines of Judaism; rather, his reach is worldwide (Jesus said, "Go into all the world in your disciple making"), because he loves all people groups equally. In other words, he is no respecter of persons.
SAVING LOVE, AND SANCTIFYING LOVE
Third, we need to distinguish, on the one hand, between God's love for all people groups everywhere as he reaches out to them through instrumentalities like you and me with the message of salvation, and his love as it is expressed in his relationship with his children who have become his children through the new birth, on the other hand.
I resort to analogy. Suppose a childless couple is searching for a child to adopt. Perhaps they cast their gaze initially at the plight of, say, South Korean special-needs babies who have been abandoned by their parents and put into a "drop box" at the house of a South Korean pastor. (This part of the analogy is based on fact.)
This couple's heart goes out to all the abandoned babies. As they look at the pictures of the various babies whom they are eligible to adopt, their hearts melt as they read about each baby's special needs, and they wish they could adopt a dozen babies! If, however, they arrive at an inner peace in adopting just one baby, their love for all the babies begins to be channeled to but one baby: the baby they have chosen to adopt.
What has changed? For one thing, their focus has gone from the many to the one. Let us say that even after adopting their one special-needs baby, they keep in touch with the orphanage, perhaps by bestowing large financial gifts on a regular basis to the ministry. Their tangible gifts are an expression of love for the babies yet to be adopted, and yet as time passes, their love for the one child grows and blossoms into a love which only these two parents can feel and express toward this single, solitary, and unique child.
The story may have a happy ending, then again it may have a not-so-happy ending. If the latter pertains, and the child grows up to be a rebellious and wayward child who becomes estranged from his or her parents, will the parents love the child any less? Not normally. They will pray for reconciliation with their child and at the same time channel their love into the lives of other people whom God sends their way.
The main idea of the analogy should be clear by now, particularly if the adopted child grows up to make the adoptive parents proud. Perhaps the child has become a Christian believer, obeying and honoring both God and parents. The child, in growing into adulthood, becomes a responsible member of society and continues to nurture the relationship with his or her adoptive parents to the point where the child, now an adult, feels free to pour out his or her heart to the parents when life throws the child some difficult trials and temptations. The more the child leans on his or her parents, the stronger the bond between them becomes.
Should the parents die and leave their adoptive child with an estate worth millions, would anyone dare accuse the parents of favoritism or of playing favorites? Not likely. In fact, once people know of the special relationship the parents and their child had, they would understand perfectly why the parents bequeathed a fortune to the child.
In similar fashion, God, too, loves all the orphans in the orphanage I've described above. However, as He begins to adopt children, one child at a time, into his forever family, God and his adoptee begin to form a loving bond which becomes an ever-expanding blessing to the child but also an ever-expanding glory to God, as the adoptee grows into a mature, godly, and loving adult.
In my analogy we have an illustration of how God's love works. Take the love the parents in the analogy feel and express, and multiply it a bazillion times over, and that is the kind of love God proffers to everyone, whether Jew or Gentile, slave or free, male or female, rich or poor, or either one of any contrasting labels you'd care to attach to people. (God, of course, does not label or pigeonhole people the way we do!)
As children are added to God's family, not every child grows up to be a King David, whom the Scripture describes as "a man after God's own heart" (see Acts 13:22), or a John the apostle, whom Jesus loved (see John 13:33), or a Mary, Martha, or Lazarus (see John 11:5), or the rich young ruler (see Mark 10:17-22, esp. v.21). Can we infer from the examples I've just listed that God indeed does "play favorite"? Of course not.
There is a principle in the Bible which brings my answer to a close, and it is this: just like the adoptive parents in my analogy drew increasingly close to their adoptive child as their relationship deepened, so also God draws increasingly close to his children who passionately seek after him. How many of us can say along with King David,
As the deer pants for the water brooks, So my soul pants for You, O God" (Psalm 42:1 NAS)?
Or who, like John, leaned on Jesus' breast (John 21:20); or like Mary, Martha, and Lazarus opened their home to Jesus on a regular basis (Luke 10:38); or like the rich young ruler bowed the knee to the man he called "Good Teacher"?
Perhaps the verses which summarize best the notion that God's love for people, though differing in some aspects based on the closeness of the bond between a given person and his or her God, are at least two in number.
"You will seek Me and find Me when you search for Me with all your heart" (Jeremiah 29:13 NAS).
"He who has my commandments and keeps them, he it is who loves me; and he who loves me will be loved by my Father, and I will love him and manifest myself to him" (John 14:21 RSVA).
Matthew 5:44-48 44 But I say to you, Love your enemies and pray for those who persecute you, 45 so that you may be sons of your Father who is in heaven. For he makes his sun rise on the evil and on the good, and sends rain on the just and on the unjust. 46 For if you love those who love you, what reward do you have? Do not even the tax collectors do the same? 47 And if you greet only your brothers, what more are you doing than others? Do not even the Gentiles do the same? 48 You therefore must be perfect, as your heavenly Father is perfect.
The Lord commanded us to love our enemies, so I know God must also. However, the Lord does make a distinction for those who keep His commands indicating greater love for those people.
John 15:9-10 9 As the Father has loved me, so have I loved you. Now remain in my love. 10 If you keep my commands, you will remain in my love, just as I have kept my Father’s commands and remain in his love.
Gal 3:28: "There is neither Jew nor Gentile, neither slave nor free, nor is there male and female, for you are all one in Christ Jesus"
More or less this. We are equal in the sense that we are one. He loves us as a whole, and he loves entirely, individually.
However, a lot of good theology has been done on the 'preferential option' for the poor, marginalized, and those who suffer most as a result of our sin. Christ flips out at the temple because people were fleecing the poor for sacrifices. He steps in on behalf of the woman at the well when the crowd was prepared to kill her. His whole beef with the religious rulers was that they were maintaining religion as a means of personal elevation, using their text to exclude and shun "gentiles" while completely missing the heart of the text. Same as how it goes today, I suppose. So for some of us, tougher love than others.
Your question revolves around the law of love.
For God so loved the world that he gave his one and only Son, that whoever believes in him shall not perish but have eternal life.
The above verse says, God loves everyone in this world, the saint and the sinner.
He Himself is the propitiation for our sins; and not for ours only, but also for those of the whole world.
1John 2:2 ISV
God loved so much everyone equally. Everyone commit sins, but not on the same level and same amount of sin. Everyone is different from human evaluation, but God died for the sins of whole world not only for some righteous.
3This is good and acceptable in the sight of God our Savior, 4who desires all men to be saved and to come to the knowledge of the truth.
1Timothy 2:3-4 ESV
This also implies God wants everyone to be saved through his love.
He causes his sun to rise on the evil and the good, and sends rain on the righteous and the unrighteous.
Matthew 5:38 ESV
Sunshine and Rain are not considered to be a negative events here, They are basic requirement for food. Jesus here portrays the God's undiscriminating love to all people. God doesn't love only the righteous, but everone equally.
For if you love those who love you, what reward have you?, says Matthew 5:46. This statement will become false, if his love towards us is not equal.