If you look at the Book of 2 Thessalonians in Chapter 3, beginning with verse 6, it says,
"But we command you, brethren, in the name of our Lord, Jesus Christ, that you withdraw from every brother who walks disorderly and _not according to the tradition which he received from us."
Then Paul continues in verse 10 what he's been discussing from verses 7 - 9, which concludes in 10,
"For even when we were with you, we commanded you this: if anyone will not work, neither shall he eat. 11 For we hear that there are some who walk among you in a disorderly manner, not working at all, but are busybodies. 12 Now those who are such we command and exhort through our Lord Jesus Christ that they work in quietness and eat their own bread.
13 But as for you, brethren, do not grow weary in doing good."
Anyway, Paul gives a few examples (of which I cannot find in my actual Bible nor my phone app Bible and for which I apologize) that basically says that whether by word or by epistle (the written documents that are letters to different churches in different countries) that they neither add nor subtract a single word of the Gospel of Jesus Christ, which, in those days, they were like what we today might consider OCD, so basically extremely meticulous in memorizing the Old Testament for most of their lives up to that point, and continued to do the same thing with the Gospel or Good News of Jesus Christ.
Luke was a physician who was responsible for, obviously, the Gospel of Luke, but also, Acts, which is the chronicle of the early church and their Acts, but it is, basically from about the 8th or 9th chapter to the end, the chronicle of Saul of Tarsus who was feared as the killer and/or capture and imprisonment of the early Christians. And he was confronted by Jesus and he changed his name to Paul. But he was steeped in tradition from almost birth! A Roman citizen, a Pharisee of the Jewish church and so he was one of those who knew huge parts of the Old Testament and so when he was saying that they should stick to the traditions that he and other Apostles and disciples had taught them.
So, whomever he had told these instructions, they knew that they were to try to follow the 10 Commandments as well as you can, as well as the other 2 Jesus said, Loving one another as He had loved them, and go and make disciples of the nations of the world about the Salvation of Jesus' message which is the main part of the Gospel word, of course.
So, yeah, they took all of that into account when he said that. But the other crucial thing is that he saved them because He said that NOBODY (besides Him who had never sinned) could follow the 10 Commandments. And God basically says that there must be blood... there must be something much more than killing animals. Someone, everyone, you, me, we all have to pay with our very lives. But Jesus stepped in and said, "I will pay the bill." So "He who knew no sin became sin [even before we knew who he was!] for us while we were yet still sinners." Everybody who accepts and believes that Jesus is who He says He is, and that He died for them—for US, and admits that they have sinned, and accepts His Salvation as payment in place of us, will go to Heaven. And try to be/do the best that you can, and when you—when we slip (and WE WILL slip....a lot) admit it to Jesus and turn from or repent (say sorry), thank Him for being our Savior, and go on about your life. There are no Good people going to Heaven, only Saved Sinners. That's it.
Hope that helps you. God Bless you and anyone who reads this.