John Gill Commentary 1 Kings 2:6

"Do therefore according to thy wisdom, and let not his hoar head go down to Sheol in peace." — 1 Kings 2:6 (ASV)

Do therefore according to your wisdom
Which though young began to appear in him, even in the life of his father; he therefore exhorts him to use the wisdom he had, and take the first and fittest opportunity to cut him off for his former murders and late treason, as a dangerous man to his government and the peace of it:

and let not his hoary head go down to the grave in peace ;
that is, let him not die a natural, but a violent death; and let not his grey hairs be any argument for sparing him, or any reason for delaying the taking of him off, because he would in course die quickly; for he must be now an old man, as old as David, or perhaps older; since he had been his general forty years, even all the time of his reign; see (2 Samuel 2:13) .