Acts 21:22-24

The elders’ plan aimed to prove to the Jewish Christians in Jerusalem, and to all the Jews there, that Paul had not abandoned the customs of the Jews. He had, of course, ceased to believe and teach that salvation came by obeying the Mosaic Law. He was no longer a Jew in religion, but he was still a racial Jew and as such observed Jewish cultural practices (e.g., a ritual of purification for those who came from foreign, unclean lands; cf. Numbers 19:12). Many commentators believed the vow in view here was a Nazarite vow, but that vow could not be taken for less than 30 days. [Note: Mishnah Oholot 2:3; 17:5; 18:6. See Haenchen, p. 612.]

The four men in question had taken a temporary vow, as Paul had done earlier (Acts 18:18). At the end of the vow each of them had to bring an offering to the temple (cf. Numbers 6:14-15). The elders suggested that Paul go with them to the temple, purify himself with them for temple worship, and show his support of the Jewish custom by paying for their offerings. Paul could do this, and did so, without compromising his convictions since the Jews did not regard taking a vow as essential for acceptance by God. It was strictly voluntary. They regarded circumcision, on the other hand, as essential. However, Paul did not even object to circumcision as a custom (Acts 16:3), though he did object to it as a rite essential for God’s acceptance (Galatians 2).