Acts 18:3

(3) We may add to this motive the principle on which St. Paul acted of being “all things to all men,” and, therefore, as a Jew to Jews (1 Corinthians 9:20). A Nazarite vow would testify to all his brethren by blood that he did not despise the Law himself nor teach other Jews to despise it. (See Notes on Acts 21:21-24.) Such a vow, involving, as it did, for a time a greater asceticism than that of common life, furnishes a link in the succession of thoughts in 1 Corinthians 9:22-25, between the Apostle’s being made “all things to all men” and his “keeping under his body, and bringing it into subjection.”