1 Samuel 1:11-13

11 And she vowed a vow, and said, O LORD of hosts, if you will indeed look on the affliction of your handmaid, and remember me, and not forget your handmaid, but will give to your handmaid a man child, then I will give him to the LORD all the days of his life, and there shall no razor come on his head.

12 And it came to pass, as she continued praying before the LORD, that Eli marked her mouth.

13 Now Hannah, she spoke in her heart; only her lips moved, but her voice was not heard: therefore Eli thought she had been drunken.