17 Then Saul said to David, "Here is my elder daughter Merab; I will give her to you for a wife; only be valiant for me and fight the Lord'S battles." For Saul thought, "Let not my hand be upon him, but let the hand of the Philistines be upon him." 18 And David said to Saul, "Who am I, and who are my kinsfolk, my father's family in Israel, that I should be son-in-law to the king?" 19 But at the time when Merab, Saul's daughter, should have been given to David, she was given to A'driel the Meho'lathite for a wife. 20 Now Saul's daughter Michal loved David; and they told Saul, and the thing pleased him. 21 Saul thought, "Let me give her to him, that she may be a snare for him, and that the hand of the Philistines may be against him." Therefore Saul said to David a second time, "You shall now be my son-in-law."
Matthew Henry's Commentary on 1 Samuel 18:17-21
Commentary on 1 Samuel 18:12-30
(Read 1 Samuel 18:12-30)
For a long time David was kept in continual apprehension of falling by the hand of Saul, yet he persevered in meek and respectful behaviour towards his persecutor. How uncommon is such prudence and discretion, especially under insults and provocations! Let us inquire if we imitate this part of the exemplary character before us. Are we behaving wisely in all our ways? Is there no sinful omission, no rashness of spirit, nothing wrong in our conduct? Opposition and perverseness in others, will not excuse wrong tempers in us, but should increase our care, and attention to the duties of our station. Consider Him that endured contradiction of sinners against himself, lest ye be weary and faint in your minds, Hebrews 12:3. If David magnified the honour of being son-in-law to king Saul, how should we magnify the honour of being sons to the King of kings!