Acts 21:23

Therefore do this that we tell you: {we have} four men who have [taken] a vow upon themselves.

Acts 18:18

So Paul, [after] remaining many days longer, said farewell to the brothers [and] sailed away to Syria, and with him Priscilla and Aquila. He shaved [his] head at Cenchrea, because he had [taken] a vow.

Numbers 6:2-7

"Speak to the {Israelites} and say to them, 'When a man or a woman takes a special vow, a vow of a {Nazirite}, to keep separate for Yahweh,

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
So Paul, [after] remaining many days longer, said farewell to the brothers [and] sailed away to Syria, and with him Priscilla and Aquila. He shaved [his] head at Cenchrea, because he had [taken] a vow.
Numbers 6:2
"Speak to the {Israelites} and say to them, 'When a man or a woman takes a special vow, a vow of a {Nazirite}, to keep separate for Yahweh,