Synopsis of the Books of the Bible, by John Nelson Darby, [1857-62], at sacred-texts.com
Psalm 57 looks more at the evil and the feet being kept, leaning on the word. This psalm, while crying to God in the same spirit and circumstances, and under the same title, is more the expression of confidence in God as a refuge. His wings are a covert till the evil be overpast, and full deliverance is looked for by His gloriously putting an end to the trial. God will send from heaven and deliver. Hence the end of the psalm is more triumphant than that of Psalm 56. He will praise among the peoples and various tribes of the earth, for God's mercy and truth are great. God's publicly exalting Himself above heaven and over all the earth is looked for. No help was on earth, none to be looked for; but this cast more entirely on God, and thus brought out a fuller confidence in His safeguard, and in the final display of power in deliverance. So it ever is. God would send from heaven. How this directs the remnant upwards, and links them with a heavenly deliverance. Then Jehovah is praised.