1 Samuel 18:17-19

17Saul said to David, ‘Here is my oldest daughter Merab. I will let you marry her. But you must be a brave soldier and you must fight battles for the Lord.’ Saul thought to himself, ‘I will not have to kill David myself. The Philistines will do that.’

18But David said to Saul, ‘I am not an important person. My family and my father's clan are not important either. I do not deserve to marry the king's daughter.’

19When the time came for Merab to marry David, Saul told her to marry a different man. He gave her to Adriel from Meholah to be his wife.