Adam Clarke on Psalms 17:7

Show thy marvellous lovingkindness - David was now exposed to imminent danger; common interpositions of Providence could not save him; if God did not work miracles for him, he must fall by the hand of Saul. Yet he lays no claim to such miraculous interpositions; he expects all from God's lovingkindness.

The common reading here is הפלה חסדיך haphleh chasadeycha, "distinguish thy holy ones;" but הפלא haple, "do wonders," is the reading of about seventy MSS., some ancient editions, with the Septuagint, Vulgate, Chaldee, Syriac, and Arabic. The marginal reading of this verse is nearer the original than that of the text.