Psalms 21:10,11 - Joseph Benson’s Commentary on the Old and New Testaments

Their fruit shalt thou destroy Their children. God will take away both root and branch; the parents and all that wicked race. For they intended evil against thee That is, against God; not directly, but by consequence, because it was against David, whom God had anointed, or against the Messiah, of whom he was a type, and against the Lord's people, injuries done to whom, God takes to be done to himself, Zechariah 2:8. They imagined a mischievous device, which they are not able to perform This clause seems to be added to teach us this great and necessary lesson, that men are justly punished by God for their wicked intentions, although they be hindered from the execution of them, contrary to what some Jewish doctors, and others, have taught. “Vengeance came upon the Jews to the uttermost, because of their intended malice against Christ. They, like Joseph's brethren, thought evil against him, but they were not able to perform it, for God meant it unto good, to bring it to pass, as it is this day, to save much people alive, Genesis 50:20. So let all the designs of ungodly men against thy church, O Lord, through thy power of bringing good out of evil, turn to her advantage; and let all men be convinced that no weapon formed against thee can prosper.”