1 Kings 2:36 - Joseph Benson’s Commentary on the Old and New Testaments

Go not forth thence any whither Solomon, it is likely, suspected Shimei's loyalty and fidelity, and therefore ordered this, 1st, for his own security. For by confining him to the royal city, he would have him always under his eye, and in a place where, as in a public theatre, all his words and actions would be narrowly observed. And by removing him from that part of the country where his kindred, and estates, and interest lay, to a place where he was almost a stranger, and yet sufficiently odious for his former and never to be forgotten insolence toward his lord and king, he would be rendered utterly incapable of raising any tumults or seditions. Solomon enjoined this, 2d, as a kind of penalty for his former wickedness, wherein yet there was more mercy than justice, and from which David had not promised him any security, but had only given him his life for the present, or during his own life and reign.