21:24 purify yourself . . . expenses. This was the Nazirite vow (Num. 6:1–21), during which the devotee let his hair grow. When the period of the vow was over, he shaved off his hair, dedicated it to the Lord, and burned it together with the sacrifice for the fellowship offering (Num. 6:18). Paul paid the expenses for four Nazirites, went to the priest with them for the sacrifices, and participated in the purification rites. In this way Paul publicly demonstrated that he was a law-abiding Jew.