Augustine of Hippo

"For You shall set them low." For You shall rank them among those from whom in degradation and contempt You will turn away. "In Your leavings You shall make ready their countenance" [Psalm 21:12]. And in these things that Thou leavest, that is, in the desires of an earthly kingdom, You shall make ready their shamelessness for Your passion.

Exposition on Psalm 21 ↗

Ambrose of Milan

"Turned away" [is] an expression properly applied to the sinner, for "Cain went out from the face of the Lord," and the psalmist says, "You will make them turn their back." One who is righteous does not turn away from the Lord but runs to meet him and says, "My eyes are ever toward the Lord." And when the Lord said, "Whom shall I send?" Isaiah offered himself of his own accord and said, "Behold, here I am."

On Joseph the Patriarch, Chapter 3 ↗

Thomas Aquinas

And he assigns the reason for this statement, why they did not establish their counsel, saying "their back." Jerome's text is clearer: "For you shall set them as a shoulder, your boundaries firm against their face." It can happen in two ways that enemies do not establish their plans against someone. In one way, if they are conquered by him. …

Exposition on the Psalms of David ↗