"The LORD forbid that I should do such a thing to my master, the LORD's anointed, or lay my hand on him; for he is the anointed of the LORD." (1 Samuel 24:6)
Saul goes into a cave to relieve himself; David and his men are hiding deep in the same cave. His men urge him: this is the day the LORD said he would give your enemy into your hands. David creeps up and cuts off a corner of Saul's robe. But afterward his conscience troubles him: The LORD forbid that I should do such a thing to my master, the LORD's anointed, or lay my hand on him; for he is the anointed of the LORD. He rebukes his men and does not allow them to attack Saul. Saul leaves the cave; David calls after him and bows down. He shows Saul the piece of robe: I could have killed you but I did not. May the LORD judge between us. Saul is struck by this and weeps: you are more righteous than I. You have treated me well; I have treated you badly. I know that you will surely be king. Swear to me that when that happens you will not kill off my descendants.
The Catechism identifies David's refusal to touch the LORD's anointed as the principle of respect for legitimate authority even when it is unjust: the vindication of the righteous is not accomplished by the one wronged taking justice into their own hands (CCC 1902).
Brothers and sisters, David held back his hand and his conscience troubled him even for cutting the robe. The restraint that refuses to harm the person who has harmed you, when God has placed them in your power, is one of the rarest acts of virtue. Trust God to judge. Do not lay your hand on the anointed, however much they deserve it.
Lord God, give us David's restraint: the power to act and the wisdom not to, the evidence in hand and the choice to leave judgment to you. Through Christ our Lord. Amen.