And they took Absalom, and cast him into a great pit in the wood, and laid a very great heap of stones upon him: and all Israel fled every one to his tent.
Read Chapter 18
Ambrose of Milan
AD 397
What should I say of Peter, who went up to the roof at the sixth hour and learned there the mystery of the baptism of the Gentiles? On the other hand, the murderer Absalom set up a pillar to himself in the valley of the king and was thrown into a ditch when he was slain. Thus the saints go up to the Lord, the wicked go down to sin; the saints are on the mountains, the guilty in the valleys, “For he is the God of the mountains and not the God of the valleys.” - "Letter 80"
But they, as we have sometimes said before in other places, do not charge themselves with what they do to us; while, on the other hand, they charge us with what they do to themselves. For which of our party is there who would desire, I do not say that one of them should perish but should even lose any of his possessions? But if the house of David could not earn peace on any other terms except that Absalom his son should have been slain in the war which he was waging against his father, although he had most carefully given strict injunctions to his followers that they should use their utmost endeavors to preserve him alive and safe, that his paternal affection might be able to pardon him on his repentance, what remained for him except to weep for the son that he had lost and to console himself in his sorrow by reflecting on the acquisition of peace for his kingdom? - "The Correction of the Donatists 8.32"
Him. Thus was the law executed upon Absalom, Deuteronomy xxi. 18. (St. Jerome) (Menochius) -- History scarcely affords a more detestable character; and his punishment was no less terrible than instructive. He was a figure of the Jews persecuting Jesus Christ, while he gave his blood for the redemption of these his enemies, and prayed for them. As they continued obdurate, they were held up as objects of horror both to heaven and to all nations, like Absalom suspended on the tree, and rejected by heaven and earth. (Calmet)