Acts 21:23

'This, therefore, do that we say to thee: We have four men having a vow on themselves,

Acts 18:18

And Paul having remained yet a good many days, having taken leave of the brethren, was sailing to Syria -- and with him are Priscilla and Aquilas -- having shorn his head in Cenchera, for he had a vow;

Numbers 6:2-7

'Speak unto the sons of Israel, and thou hast said unto them, When a man or woman doeth singularly, by vowing a vow of a Nazarite, to be separate 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 yet a good many days, having taken leave of the brethren, was sailing to Syria -- and with him are Priscilla and Aquilas -- having shorn his head in Cenchera, for he had a vow;
Numbers 6:2
'Speak unto the sons of Israel, and thou hast said unto them, When a man or woman doeth singularly, by vowing a vow of a Nazarite, to be separate to Jehovah;