8 You were inquiring perhaps when he said, “He has sent from heaven and has saved me.” What has He sent from heaven? Whom has He sent from heaven? An Angel has He sent, to save Christ, and through a servant is the Lord saved? For all Angels are creatures serving Christ. For obedience there might have been sent Angels, for service they might have been sent, not for succour: as is written, “Angels ministered unto Him,” not like men merciful to one indigent, but like subjects to One Omnipotent. What therefore “has He sent from heaven, and has saved me”? Now we hear in another verse what from heaven He has sent. “He has sent from heaven His mercy and His truth.” For what purpose? “And has drawn out my soul from the midst of the lions' cubs.” “Hath sent,” he says, “from heaven His mercy and His truth:” and Christ Himself says, “I am Truth.” There was sent therefore Truth, that it should draw out my soul hence from the midst of the lions' whelps: there was sent mercy. Christ Himself we find to be both mercy and truth; mercy in suffering with us, and truth in requiting us....Who are the lions' whelps? That lesser people, unto evil deceived, unto evil led away by the chiefs of the Jews: so that these are lions, those lions' whelps. All roared, all slew. For we are to hear even here the slaying of these very men, presently in the following verses of this Psalm.
9. “And has drawn out,” he says, “my soul from the midst of the lions' whelps”. Why do you say, “And has drawn out my soul”? For what had you suffered, that your soul should be drawn out? “I have slept troubled.” Christ has intimated His death....
Source: The Enarrations, or Expositions, on the Psalms (New Advent)