"And she was in bitterness of soul, and prayed to the Lord and wept in anguish. Then she made a vow and said, 'O Lord of hosts, if You will indeed look on the affliction of Your maidservant and remember me, and not forget Your maidservant, but will give Your maidservant a male child, then I will give him to the Lord all the days of his life, and no razor shall come upon his head."

Samuel 1:10-11

God answered Hannah's prayer and she conceived Samuel. She filled her vow to the Lord and Samuel was taken to the temple and was entrusted to the priest. Because of her obedience, Samuel became the most famous prophet in Israel's history.