2 Then David sent out one third of the people under the hand of Joab, one third under the hand of Abishai the son of Zeruiah, Joab's brother, and one third under the hand of Ittai the Gittite. And the king said to the people, "I also will surely go out with you myself."
Matthew Henry's Commentary on 2 Samuel 18:2
Commentary on 2 Samuel 18:1-8
(Read 2 Samuel 18:1-8)
How does David render good for evil! Absalom would have only David smitten; David would have only Absalom spared. This seems to be a resemblance of man's wickedness towards God, and God's mercy to man, of which it is hard to say which is most amazing. Now the Israelites see what it is to take counsel against the Lord and his anointed.