“As the Lord liveth” was the most common form of oath among the Israelites (e. g. Judges 8:19; 1 Samuel 14:39; 1 Samuel 19:6). It was unique to David to attach a further clause to this oath - a clause of thankfulness for some special mercy 1 Samuel 25:34, or for God’s constant protection of him (here and in 2 Samuel 4:9).
Related Commentaries of 1 Kings 1:29
1 Kings 1:29
29 And the king sware, and said, As the LORD liveth, that hath redeemed my soul out of all distress,