Psalms 18:36

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 Psalms 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.