1 Kings 2:28 - Ellicott's Commentary On The Whole Bible

Joab had turned. — It is strange that Joab should have been in no danger or anxiety immediately after the actual failure of the conspiracy; and it is also notable that, although the real motive for putting him to death was to punish his support of Adonijah, now renewed, yet Solomon’s words in pronouncing sentence on him refrain from mention of anything except the old crimes dwelt upon in the dying charge of David. Possibly this was done to bring Joab’s case within the emphatic declaration of the Law, that no sanctuary should protect the wilful and treacherous murderer, and that innocent blood, so shed and left unavenged, would pollute the land (Exodus 21:14; Numbers 35:33). It is significant, moreover, of the increased power of the monarchy, even in hands young and yet untried, that the old captain of the host, who had been “too hard” for David, even before David’s great sin, should now fall, as it would seem, without a single act of resistance or word of remonstrance on his behalf, after a long career of faithful service, only once tarnished by disloyalty. It has been noticed that if (as is probable) the “Tabernacle of the Lord” at Gibeon is meant, Joab falls close to the scene of his murder of Amasa, “at the great stone in Gibeon” (2 Samuel 20:18).