John Gill's Bible Commentary Ver. 4. But the king covered his face , etc.] And would not see his generals, and thank them for their services: but wrapped himself in his mantle, after the manner of mourners: and the king cried with a loud voice, O my son Absalom! O Absalom, my son, my son ! and this was some time, perhaps some days after he had received the news of his death, since Joab and the army were returned from the battle; had it been a sudden start of passion, upon first hearing thee news, and had continued a few hours, it would have been more excusable; but to continue some days, as it is very probable it did, was very unbecoming.
Matthew Henry Commentary
Verses 1-8 - To continue to lament for so bad a son as Absalom, was very unwise, an very unworthy. Joab censures David, but not with proper respect an deference to his sovereign. A plain case may be fairly pleaded with those above us, and they may be reproved for what they do amiss, but it must not be with rudeness and insolence. Yet David took the reproof an the counsel, prudently and mildly. Timely giving way, usually prevent the ill effects of mistaken measures.
Original Hebrew והמלך4428 לאט3813 את853 פניו6440 ויזעק2199 המלך4428 קול6963 גדול1419 בני1121 אבשׁלום53 אבשׁלום53 בני1121 בני׃1121