Nazarites: On Completion of Vow: To Shave Their Heads
Source: TTT
Numbers 6:18
Then at the entrance to the Tent of Meeting, the Nazirite is to shave his consecrated head, take the hair, and put it on the fire under the peace offering.
Acts 18:18
Paul remained in Corinth for quite some time before saying goodbye to the brothers. He had his head shaved in Cenchrea to keep a vow he had made, and then he sailed for Syria, accompanied by Priscilla and Aquila.
Acts 21:24
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.