Ps 16:5

“"To perfect My steps in Your paths" [Psalm 17:5]. That the love of the Church might be perfected in the strait ways, whereby she arrives at Your rest. "That My footsteps be not moved." That the signs of My way, which, like footsteps, have been imprinted on the Sacraments and Apostolical writings, be not moved, that they may mark them who would follow Me. Or at least, that I may still abide fixedly in eternity, after that I have accomplished the hard ways, and have finished My steps in the straits of Your paths.”

“Never by our sole diligence or zeal or by our most tireless efforts can we reach perfection. Human zeal is not enough to win the sublime rewards of blessedness. The Lord must be there to help us and to guide our hearts toward what is good. Every moment we must join in the prayer of David: "Direct my footsteps along your paths so that my feet do not move astray" and "He has settled my feet on a rock and guided my footsteps"—all this so that the invisible guide of the human spirit may direct back toward love of virtue our free will, which in its ignorance of the good and its obsession with passion is carried headlong into sin.”

“Maintain: – המוך is an infinitive in the place of an imperative, as “Keep (שמור) the sabbath day” (Deut. 5:12); “Go (הלוך) and call” (Jer. 2:2). And he says: my treadings in Thy paths: – meaning, my treadings as they go in Thy paths, and in Thy way do Thou maintain. (so that) my footsteps have not slipped: – There is some disagreement as to the reading of the word נמטו (slipped). There are some MSS. which daghesh the teth, and if this be so it will be derived from a double ayin verb; there are MSS., however, (where the word appears) without the daghesh, and then it will be derived from a verb 'ayin waw.”

“Next he determines what he asks: "Perfect my steps in your paths," namely of justice. Job 4: "Where is your strength, your patience, and the perfection of your ways?" And this, so that my footsteps, that is, my affections, may not be moved from your commandments. Or Christ asks for the Church, that her steps be perfected and that her footsteps, that is, her sacraments, not be moved. Likewise, since from actions habits are generated, actions leave footsteps in the will. Or, literally, David asks that he not be hurled down from the precipices over which he passed while fleeing from Saul: 1 Sam. 24: "Saul pursued him over the steepest rocks." Another reading has: "Sustain my steps in my paths, and my footsteps will not slip." Or that Christ, according to his humanity, be perfected forever in the glory of divinity: Jn. 17: "Glorify me, Father, with yourself, with the glory that I had before the world was."”