Cross reference
Acts 21:23
23 Do this, then, which we say to you: We have four men who have taken an oath;
Acts 18:18
18 And Paul, after waiting some days, went away from the brothers and went by ship to Syria, Priscilla and Aquila being with him; and he had had his hair cut off in Cenchrea, for he had taken an oath.
Numbers 6:2-7
2 Say to the children of Israel, If a man or a woman takes an oath to keep himself separate and give himself to the Lord;
3 He is to keep himself from wine and strong drink, and take no mixed wine or strong drink or any drink made from grapes, or any grapes, green or dry.
4 All the time he is separate he may take nothing made from the grape-vine, from its seeds to its skin.
5 All the time he is under his oath let no blade come near his head; till the days while he is separate are ended he is holy and his hair may not be cut.
6 All the time he is separate he may not come near any dead body.
7 He may not make himself unclean for his father or his mother, his sister or his brother, if death comes to them; because he is under an oath to keep himself separate for God.