I respectfully say, Strictly speaking, there is no biblical basis for holding this assumption as fact.
In this answer:
- A Scriptural Answer - The Formula [How we interpret the bible through comparisons]
- The Little Flock, Distinct from the Great Flock
- A Hidden Pearl [144,000] in the Parable of the Faithful and Discreet Slave
- Significance of the Money Weights [Atonement, justice, bought from the earth]
- Significance of a "Name" in the Bible, and the Sealing on Foreheads
- How It Ties Together
- Chosen today, or in a future covenant?
- In Answer to Your Question
The idea that there are classes of 'heavenly callings' could be justified in the 12 × 12,000 in Revelation 7. But this strongly suggests a separate calling or attainment than the 'innumerable' class holding the palm branches.
An acceptable answer needs to harmonize this (apparent) conflict,
without introducing non-scriptural information, ignoring anything
relevant or contradicting other scriptures.
This is a deep riddle, something I've explored for some time. I'll attempt to convey the answer here:
A Scriptural Answer - The Formula
Revelation is a book of signs, parables, and puzzles. Virtually every sentence somehow relates to the previous books of the bible. Its the grandest of riddles.
To understand this one issue you inquire of, we should take a very strict stance on interpretation:
1 The proverbs of Solomon son of David, king of Israel:
2 for gaining wisdom and instruction; for understanding words of insight;
3 for receiving instruction in prudent behavior, doing what is right and just and fair;
4 for giving prudence to those who are simple, a knowledge and discretion to the young—
5 let the wise listen and add to their learning, and let the discerning get guidance—
6 for understanding proverbs and parables, the sayings and riddles of the wise.
Solomon prefigured Jesus, the Word. While Solomon's inspired wisdom encompassed only a few writings, the greater Solomon, Jesus, delivered the entire bible to us. Hence, to solve his riddles, you must learn his wisdom. Its no small task, and yet it can be done.
In Revelation, Jesus states "Let him that has ears, listen.". As you become familiar with Jesus' way of speaking, you would recognize that to mean "This is a puzzle, solve it.", or "This will evade your understanding unless you really ponder it.".
The Little Flock, Distinct from the Great Flock
The first great and obvious clue to a separation between heavenly classes is here:
Luke 12: 32 - 34:
32 “Do not be afraid, little flock, for your Father has been
pleased to give you the kingdom. 33 Sell your possessions and give
to the poor. Provide purses for yourselves that will not wear out, a
treasure in heaven that will never fail, where no thief comes near
and no moth destroys. 34 For where your treasure is, there your heart
will be also.
- Distinct little flock is mentioned.
- It inherits a kingdom.
- A parable to 'treasure' is provided [very important to the subject].
Hence you see a contrast between a great and little flock, with inheritance of the kingdom in view.
A Hidden Pearl [144,000] in the Parable of the Faithful and Discreet Slave
A reader of Matthew 25 might make an intuitive connection between a "great and little flock" at work in that Jesus has multiple slaves - one entrusted with greater wealth than the other. [we will not consider the evil slave in this scope].
It is very important to remember that these parables are in fact riddles, the same as Revelation. These riddles are sometimes exploited for personal human glory, but it is in fact a prophetic parable involving specific weights and numbers.
Note: 1 talent = 60 minas = 3600 shekels = 72000 Gerahs [Ezekiel 45:12]
SLAVE 1: 360,000 Gerahs entrusted:
5 × 72,000 = 360,000
SLAVE 2: 144,000 Gerahs entrusted:
2 × 72,000 = 144,000
It should be alarming that both numbers in themselves are highly unique: 360,000 being a perfectly round number, and 144,000 being the one in question from revelation.
Banking on numerical coincidences is not enough to prove meanings - people have been doing this for generations. The symbols must have meaning.
Remember the key point Jesus gave, anchoring the "business" aspect of the parable:
Sell your possessions and give to the poor. Provide purses for
yourselves that will not wear out, a treasure in heaven that will
never fail, where no thief comes near and no moth destroys.
To emphasize it again, the little flock is encouraged in the proper way to do business and make a heavenly profit. Yet, if this were not enough to anchor the 'little slave' to the 'little flock' in the '144,000' puzzle, there is more.
What is the significance of the weights in question: The talents, minas, shekels, and gerahs?
Significance of the Money Weights
Talents in themselves are distinctly related to the heavy weight of sin [see Matthew 18]. In the ancient money system, a talent was a very heavy sum of money. Literally, judged in weight. Further, Belshazzar was found guilty in his dealings where a parable of money weights was given. He was weighed in the balance and found to be deficient. In his case, a less weighty comparison was made in Minas and shekels.
Still, the relationship of forgiveness to money, and money to atonement, is further supported in Exodus 30:11-16:
11 Then the Lord said to Moses, 12 “When you take a census
[Revelant to the sealing number in Revelation] of the Israelites to
count them, each one must pay the Lord a ransom for his life at the
time he is counted [the master then summon his slaves to see what
they gained via their work]. Then no plague will come on them when you
number them. 13 Each one who crosses over to those already counted is
to give a half shekel, according to the sanctuary shekel, which
weighs twenty gerahs. This half shekel is an offering to the Lord.
14 All who cross over, those twenty years old or more, are to give an
offering to the Lord. 15 The rich are not to give more than a half
shekel and the poor are not to give less when you make the offering to
the Lord to atone for your lives. 16 Receive the atonement money from
the Israelites and use it for the service of the tent of meeting. It
will be a memorial for the Israelites before the Lord, making
atonement for your lives.”
In this passage you see a number of points:
- The relationship between money and forgiveness.
- The significance of the shekel, as a weight of Gerahs (as above, you see 144,000 Gerahs entrusted to the second slave)
- This involves redemption, or repurchasing to the Lord, harmonizing with Revelation 14:4 where it states they are "bought" from the earth.
- It has to do with a census, or numbering of those saved.
Significance of a "Name" in the Bible, and the Sealing on Foreheads
A good name is better than fine perfume, and the day of death better
than the day of birth.
“‘I know your works. You have the reputation of being alive, but you
are dead. Wake up, and strengthen what remains and is about to die,
for I have not found your works complete in the sight of my God.
A NAME before God is the sum of a person's works. As seen above, works are judged through a symbolic system of money values. The 144,000 earn a name through works which are the reflection of their leader, Jesus. They have the name on their forehead as a result of their fine works.
In the same way, let your light shine before others, that they may see
your good deeds and glorify your Father in heaven.
Thus, the the bible parables a name is works, and works are the name - good or bad, Godly or Satanic.
Having the name of the Lord on your forehead means that you've accepted his ransom and performed his works.
For further proof the the name-to-works concept, Jesus elaborates on it via the related Sheep/Goats parable (given after the faithful steward parable)
34 “Then the King will say to those on his right, ‘Come, you who are
blessed by my Father; take your inheritance, the kingdom prepared for
you since the creation of the world. 35 For I was hungry and you gave
me something to eat, I was thirsty and you gave me something to drink,
I was a stranger and you invited me in, 36 I needed clothes and you
clothed me, I was sick and you looked after me, I was in prison and
you came to visit me.’
Compare: 1 John 3:17, James 2:15, Luke 12:32-34 [Three concepts that harmonize the role of a true Christian under his master]
How It Ties Together
The 144,000 are a class of people who have done the works of their master to perfection. They are taken from the tribes of Israel, and judged on a symbolic system of money representing works. In this way they do business, and are also purchased [a parable within the ransom relationship, to give what you've been given, namely forgiveness and the means to life]. Their primary objective is to care for the poor, as further portrayed in the Stewards parable. The fact that they are first-fruits seems to illude to them being the first to qualify as worthy in Jesus' eyes.
They are distinct from the great flock in that they are lesser in accomplishments, yet more is given to them. Consider Jesus "First last, last first" sayings.
The details of the great flock are not a part of your question, other than to show whether or not the 144,000 is a literal number or not, and distinct from the 144,000.
Chosen today, or in a future covenant?
Its especially noteworthy to see that they are chosen from the tribes of Israel, something we modern Christians think as rejected and unworthy. Some would say this illudes to a spiritual Israel, and have assumed the title "Anointed, or Faithful and Discreet Slave" [“Do not become discreet in your own eyes.” (Rom. 12:10, 16)]
We should mind Jesus standards for greatness, speaking of John the Baptiser:
I tell you, among those born of women there is no one greater than
John; yet the one who is least in the kingdom of God is greater than
he." - Luke 7:28
We should keep in mind that God's justice will be worked out during Christ's millenial reign, and its possible that new arrangements and covenants will be given. Isaiah 48
In Answer to Your Question
What is the biblical basis for the JW belief that only 144,000 go to heaven?
For one to say "There is no biblical basis for the JW claim" is not enough, since it must be scripturally proven or disproven as you've mentioned.
As you can see, great discipline and care should be taken in how the interpretations of such things are derived, especially when one feels it applies to their own personal glory.
The answer is, the biblical basis for their claim is questionable and somewhat speculative. Yet one could say the same of my answer. It seems implied through the scriptures that many have a heavenly hope, although different callings are implied.
In the end, the final answer will be as the yet another faithful steward [entrusted with the feeding of many] so perfectly put it:
Genesis 40:8 "Do not interpretations belong to God?"