Actually, they quoted Scripture, verses 16-18, and then made their decision based on the fact that the OT regulations had been fulfilled in Christ who commissioned baptism rather than circumcision as the entrance into the household of God. So Paul didn’t set aside Scripture, rather he laid the matter before the leaders of the Church who debated the theological implications, cited Scripture as a witness, and then made their decision, which is the same way the Church has done it down through the centuries, up to and including our own day.
@ brb3 The Bible is the witness to Christ and his Church, which cannot be separated. As G. K. Chesterton cited, one cannot rip a holy book out of the hands of those who wrote it and then claim you will accept the book but not the religion that produced it. The Bible is the product of God’s people, the Israelite prophets and partriarchs as well as the Apostles and a few of their disciples , who were the spiritual descendants of the OT saints to whom God spoke. The Bible was not written to be a proof text for doctrines, but a help and a guide for the Church as a part of the whole of Sacred Tradition which consists of the Bible, the Church Fathers, and the living Magisterium–the bishops united to the Holy Father.