Numbers 30:8

When a young Hebrew woman married, her husband gained authority over her. He could cancel any vow or pledge she made while under her father's authority. This was only true if he canceled it as soon as he heard about it.

Vows were an important way to show devotion or piety. But people sometimes made them quickly and forgot them. People often made voluntary pledges during special religious events or in times of war. The mention of vows and voluntary offerings might have led to further discussion here (29:39; compare 15:3; see also 6:1–21; Leviticus 5:4–5; 27:1–34; Deuteronomy 23:21–23).

These instructions applied to Hannah and Elkanah (1 Samuel 1:1–28). Such practices, including fasting, continued into the New Testament period (for example, Matthew 6:16; 15:3–9; Acts 18:18; 21:23). Vows made by females needed approval from the responsible male who would share financial responsibility for the vow. This applied to young and unmarried or adult and married women. No one, male or female, young or old, should make a vow to God and then ignore it.