2 And David sent forth the army, one third under the command of Jo'ab, one third under the command of Abi'shai the son of Zeru'iah, Jo'ab's brother, and one third under the command of It'tai the Gittite. And the king said to the men, "I myself will also go out with you."
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.