*Minor differences ignored. Grouped by changes, with first version listed as example.
Thou hast enlarged my steps under me - The idea here is, "Thou hast made room for my feet, so that I have been enabled to walk without hindrance or obstruction. So in Psalm 31:8, "Thou hast set my feet in a large room." The idea is, that he was before straitened, compressed, hindered in his goings, but that now all obstacles had been taken out of the way, and he could walk freely.
That my feet did not slip - Margin, mine ancles. The Hebrew word here rendered in the text feet, and in the margin ancles, means properly a joint; small joint; especially the ancle. The reference here is to the ancle, the joint that is so useful in walking, and that is so liable to be sprained or dislocated. The meaning is that he had been enabled to walk firmly; that he did not limp. Before, he had been like one whose ancles are weak or sprained; now he was able to tread firmly. The divine favor given to him was as if God had given strength to a lame man to walk firmly.
Enlarged my steps - See on Psalm 18:19 (note). From the hand of God he had continual prosperity; and while he walked with God no enemy was able to prevail against him. He details his successes in the following verses.
Thou hast enlarged my steps under me,.... Which is opposed to those straitened circumstances in which the psalmist was, Psalm 18:4; and is expressive of deliverance from his enemies, by whom he was surrounded, besieged, and shut up; see Psalm 31:8; and of freedom of walking at large, without being straitened for room, or interrupted by others, Proverbs 4:12; and of safety in standing; all which is true in a spiritual sense of believers in Christ, who being delivered by him out of the hands of their enemies, serve the Lord without fear in righteousness and holiness; walk at liberty by faith in Christ, and up and down in the name of the Lord their God; and have their feet established upon the Rock of ages, that sure and large foundation, Christ, from which there is no danger of slipping and falling; as follows;
that my feet did not slip; so as to fall and perish; for sometimes the steps of the saints are well nigh slipped; yea, in some sense they stumble; slip, and fall, but not so as to be utterly cast down and perish eternally; the bottom on which they are is so broad, and the foundation so sure, that it is not possible they should. The words will bear to be applied to Christ, who was in very pressed and straitened circumstances, when beset with the bulls of Bashan, encompassed with dogs, and enclosed with the assembly of the wicked; and was in slippery places, when he sunk in deep mire where there is no standing, Psalm 22:12; but now being delivered from all this, he is brought, as in Psalm 18:19, into a large place, into heaven, and made higher than the heavens, and is set down at the right hand of God, from whence he can never be moved.
enlarged my steps--made ample room (compare Proverbs 4:12).
Slipt - As they are apt to do in narrow and uneven ways.
*More commentary available at chapter level.