Matthew Poole and continuators on 2 Samuel 14:29

29 Therefore Absalom sent for Joab, to have sent him to the king , but he would not come to him: and when he sent again the second time, he would not come .

That by his mediation he might be admitted into the Kings favour and presence.

Partly, because perceiving David's affections to be cold to Absalom, he would not venture his own Interest for him, especially in desiring that which he feared he should be denied; partly, lest by interceeding further for Absalom, he should revive the remembrance of his former Murther, and meet with the reproach of one Murtherers interceeding for another; and partly, because by converse with Absalom, he observed his temper to be such, that if once he were fully restored to the Kings favour, he would not onely eclipse and oppose Ioab's interest and power with the King, but also attempt high things, not without danger to the King and Kingdom, as it happened.