When one of the men saw this, he told Joab, “I just saw Absalom hanging in an oak tree!”
Here is Absalom quite at a loss, at his wit's end first, and then at his life's end. He that began the fight, big with the expectation of triumphing over David himself, with whom, if he had had him in his power, he would not have dealt gently, is now in the greatest consternation, when he meets the servants of David, Sa2 18:9.
Commenting on 2 Samuel 18:9-18
And a certain man saw it,.... Saw him in the above posture, one of David's soldiers: and told Joab, and said, behold, I saw Absalom hanged in an oak; caught by the neck in one, out of which he could not disengage himself, but there he hung, though alive.
I saw Absalom hanged in an oak - He must have hung there a considerable time. this man saw him hanging; how long he had been hanging before he saw him, we cannot tell. He came and informed Joab; this must have taken up a considerable time. Joab went and pierced him through with three darts; this must have taken up still more time.