How do you know this??? How do you know they returned to Jerusalem??? Is that a tradition they passed on from one generation to the next???
We know this because that tradition was recorded as scripture by the apostle Paul...And preserved by God for a couple of millenniums so far...You don't have an argument...
The Church teaches Scripture just fine. The Church gave us Scripture. Therefore, the Church is its guardian and faithful interpreter. Your basic model of Scriptural understanding is flawed.
Well, I understand the following scripture...
Eph 3:3 How that by revelation he made known unto me the mystery; (as I wrote afore in few words,
Eph 3:4 Whereby, when ye read, ye may understand my knowledge in the mystery of Christ)
2Ti_2:7 Consider what I say; and the Lord give thee understanding in all things.
1Jn_5:20 And we know that the Son of God is come, and hath given us an understanding, that we may know him that is true, and we are in him that is true, even in his Son Jesus Christ. This is the true God, and eternal life.
So that stuff is a little tough for you, eh??? You Don't Get It...Your religion has to tell you what those scriptures mean and they mean that your religion will provide the understanding, and not God...
Good luck with that...
It wasn't "recorded as Scripture by the Apostle Paul". Nothing was "Scripture" when it was "recorded". It became Scripture, subsequently.
The essential point here is the indisputable fact that Paul and Barnabas returned to Jerusalem to resolve a pastoral and theological issue, with the "apostles and ancients" without recourse to a then non-existent New Testament. They could do so by virtue of the authority bestowed on them by Jesus himself. That authority is still to be found in the successors of the Apostles.
You have no argument.