The king said moreover to Shimei
Not as another reason for his putting him to death, but to remind him of his former sins, and to observe to him the providence of God in suffering him to fall into others, that justice might take place upon him for them also:
thou knowest all the wickedness which thine heart is privy to, that
thou didst to David my father;
which conscience must bear witness to, and accuse him of, not only of the words and actions themselves uttered and done by him, but of the malice and wickedness from whence they sprung:
therefore the Lord shall return thy wickedness upon thine own head;
the punishment of it; which though not directly inflicted for that, yet in providence was brought about as a just retaliation for it.