1 Samuel 1:10-13

And she was in bitterness of soul, and prayed unto the LORD, and wept sore. And she vowed a vow, and said, O LORD of hosts, if thou wilt indeed look on the affliction of thine handmaid, and remember me, and not forget thine handmaid, but wilt give unto thine handmaid a man child, then I will give him unto the LORD all the days of his life, and there shall no razor come upon his head. And it came to pass, as she continued praying before the LORD, that Eli marked her mouth. Now Hannah, she spake in her heart; only her lips moved, but her voice was not heard: therefore Eli thought she had been drunken.