Psalms 94:18

When I said, My foot slippeth - I can no longer stand. My strength is gone; and I must sink into the grave. The original here is, “If I say, My foot slippeth,” etc. The statement is general; that if at any time he had been, or should be, in such circumstances, then God would interpose. The general remark, however, is founded on his interposition on this particular occasion. His aid was then so marked and timely, that he felt that he could make the declaration general in regard to his whole life - to all circumstances in which he would ever be placed.

Thy mercy, O Lord, held me up - By thy merciful interposition thou didst keep me from falling. It was strength put forth as the expression of “mercy;” not strength to which he had any claim. How often in life may we say this of ourselves, that when just ready to sink; when our strength was almost gone; when a little severer pressure would have brought us to the grave, God by his mercy and his power interposed and saved us! Every such act of mercy - every new interposition in this manner - is a new gift of life, and lays us under obligation as if we had been just created, for it is just so much more of life given us by God.