1 Samuel 1:10-11

10She was very upset as she prayed to the Lord, and she was weeping uncontrollably.

11She made a vow saying, “O Lord of hosts, if you will look with compassion on the suffering of your female servant, remembering me and not forgetting your servant, and give a male child to your servant, then I will dedicate him to the Lord all the days of his life. His hair will never be cut.”