Acts 21:23

Do this, then, which we say to you: We have four men who have taken an oath;

Acts 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

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;

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, 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
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;

Basic English, produced by Mr C. K. Ogden of the Orthological Institute - public domain