On one occasion, Hannah went to the sanctuary and prayed for a child. In tears, she vowed that if she were granted a child, she would dedicate him to God as a nazirite.Eli, who was sitting at the foot of the doorpost in the sanctuary at Shiloh, saw her apparently mumbling to herself and thought she was drunk, but was soon assured of both her motivation and sobriety. Eli was the priest of Shiloh, and one of the last Israelite Judges before the rule of kings in ancient Israel. He had assumed the leadership after Samson's death.Eli blessed her and she returned home. Subsequently, Hannah became pregnant, later giving birth to Samuel, and praised God for his mercy and faithfulness.
After the child was weaned, she left him in Eli's care, and from time to time she would come to visit her son.
–Wikipedia