Psalms 57:1

The title of this psalm has one word new in it, Al-taschith - Destroy not. Some make it to be only some known tune to which this psalm was set; others apply it to the occasion and matter of the psalm. Destroy not; that is, David would not let Saul be destroyed, when now in the cave there was a fair opportunity of killing him, and his servants would fain have done so. No, says David, destroy him not, Sa1 24:4, Sa1 24:6. Or, rather, God would not let David be destroyed by Saul; he suffered him to persecute David, but still under this limitation, Destroy him hot; as he permitted Satan to afflict Job, Only save his life. David must not be destroyed, for a blessing is in him (Isa 65:8), even Christ, the best of blessings. When David was in the cave, in imminent peril, he here tells us what were the workings of his heart towards God; and happy are those that have such good thoughts as these in their minds when they are in danger! I. He supports himself with faith and hope in God, and prayer to him, Psa 57:1, Psa 57:2. Seeing himself surrounded with enemies, he looks up to God with that suitable prayer: Be merciful to me, O Lord! which he again repeats, and it is no vain repetition: Be merciful unto me. It was the publican's prayer, Luk 18:13.

— Matthew Henry's Concise Commentary (public domain)