Why did men from Jerusalem travel to Antioch?
Jewish believers in Jerusalem heard that Gentiles at Antioch were being brought into a relationship with God, so they sent men to investigate whether this was true. They wanted to check if Gentiles were being saved without becoming proselytes of Judaism or being circumcised according to Moses.
Les explains that when the Jewish believers down at Jerusalem got wind that Gentiles were being brought into a relationship with their God, they got all shook up. So they sent men from Jerusalem all the way up to Antioch to check out and see if this was really true. They were concerned that Paul, a Jew, was permitting Gentiles to claim they were saved without becoming proselytes of Judaism. The men from Judea, that is Jerusalem, taught the brethren at Antioch that except they be circumcised after the manner of Moses, they could not be saved. Later, when Paul went down to Jerusalem, he was called on the carpet, and certain Pharisees who believed still insisted it was needful to circumcise them.