Acts 15:13-21

So James here says basically what Peter says. He supports him and then he adds stuff from the Old Testament. He says, look, God prophesied way, way back in Amos and in other places, that He was going to bring the Gentiles into covenant with Him. And so he said God has known from eternity that He was going to do this. This is a great work of God and it just had exploded in their laps, and they were having to deal with it because this is the first time when God had essentially opened up salvation to the Gentiles.

So He is saying here as he concludes, let us not trouble them anymore except for these few prohibitions that he names, because they know the law. This is exactly what he says in verse 21, "For Moses has had throughout many generations, those who preach him in every city being read in the synagogues every Sabbath." So he said, we do not have to send them a great many detailed long pages of instructions about how they should conduct themselves as Christians. He is assuming here that they are becoming Christians and so he says they have Moses.