“mule.” See commentary on 2 Samuel 13:29.
“the great oak.” It is likely that after the incident with Absalom, this particular oak became well known, so here the text refers to it as “the great oak.”
“his head caught hold of the oak and he was taken up between the sky and earth.” This is a bizarre record for a number of reasons. One reason is why was Absalom, the supposed new king, riding alone? He was going into battle! He should have had armor-bearers or some kind of guard with him. He was reckless and arrogant in his life, and now that contributes to his undoing. Also, his glorious hair became a fatal liability (cp. 2 Sam. 14:25-26). Ordinarily, Absalom would not have been so careless as to ride through the tangled brush and trees without paying close attention, but unexpectantly running into a group of David’s men when he was alone no doubt distracted him, and in his haste to get out of danger he entrapped himself in the tangled branches. Like so many times in Scripture, behind this incident we see the unseen hand of God, who was fighting behind the scenes to preserve the Davidic dynasty and defeat David’s enemies (cp. 2 Sam. 17:14).