Purification of Paul, to Show his Fidelity to the Law
Source: Nav
Acts 21:24, 26
Take these men, purify yourself along with them, and pay their expenses so they can have their heads shaved. Then everyone will know that there is no truth to these rumors about you, but that you also live in obedience to the law. / So the next day Paul took the men and purified himself along with them. Then he entered the temple to give notice of the date when their purification would be complete and the offering would be made for each of them.