17 And Saul said to David, Here is my oldest daughter Merab, whom I will give you for your wife: only be strong for me, fighting in the Lord's wars. For Saul said, Let it not be through me that his fate comes to him, but through the Philistines. 18 And David said to Saul, Who am I, and what is my father's family in Israel, that I am to be son-in-law to the king? 19 But when the time came to give Merab, Saul's daughter, to David, she was given to Adriel of Meholath. 20 And Saul's daughter Michal was in love with David: and Saul had word of it and was pleased. 21 And Saul said, I will give her to him, so that she may be a cause of danger to him, and so that the hands of the Philistines may be against him. So Saul said to David, Today you are to become my son-in-law for the second time.
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!