Galatians 2:1

[Paul, having shown that his gospel was independent of the powers at Jerusalem, proceeds to prove that it was fully endorsed by them, and so he was not a false apostle, as his enemies represented him to be.] Then after the space of fourteen years [i e., after his conversion, or about A. D. 51] I went up again to Jerusalem with Barnabas, taking Titus also with me. [Paul omits his second visit to Jerusalem, which took place about A. D. 44 (Acts 11:30; Acts 12:25). It is not needful to mention this visit, for it was a brief one, and made at a time when persecution raged there, and when James, the son of Zebedee, was beheaded, and Peter cast into prison. It was no time for conference, and had no bearing whatever on Paul's apostleship or gospel. The third visit (Acts 15:1-35) had such bearings, and is therefore mentioned. Titus was among the "certain other" mentioned at Acts 15:2. Titus was a Gentile convert, and Paul evidently took him with him that he might use him to test the question as to whether circumcision was required of such converts. If Paul wrote from Corinth, Titus was then with him, a living witness of Paul's success in this test case. At this council which Paul and Barnabas attended, a decree confirming the liberty of the Gentiles was issued. Some question has arisen as to why Paul did not cite the decree to prove the correctness of his position on the question of circumcision. Paley gives an elaborate number of reasons for his not doing so, none of which are wholly satisfactory, but the real reason is very obvious. Paul could prove his apostleship easier than he could the decree, and the decree would settle only one or two questions, while the establishment of his apostleship would enable him to settle every question. Moreover, the Galatians had no doubt seen the decree and had it explained away-- Acts 16:4-6]