Acts 21:23

Therefore do this, what we say to you: We have four men who have a vow on themselves;

Acts 18:18

And Paul having remained many days more, taking leave of the brothers, he sailed from there into Syria. And Priscilla and Aquila were with him. And Paul had shorn his head in Cenchrea, for he had a vow.

Numbers 6:2-7

Speak to the sons of Israel, and say to them, When a man or a woman shall vow a vow, a vow of a Nazarite, to be separated to Jehovah,

Treasury of Scripture Knowledge

Summary

Do therefore this that we say to thee: We have four men which have a vow on them;

Bible References

We have

Acts 18:18
And Paul having remained many days more, taking leave of the brothers, he sailed from there into Syria. And Priscilla and Aquila were with him. And Paul had shorn his head in Cenchrea, for he had a vow.
Numbers 6:2
Speak to the sons of Israel, and say to them, When a man or a woman shall vow a vow, a vow of a Nazarite, to be separated to Jehovah,