John Calvin Commentary Psalms 38:16

"For I said, Lest they rejoice over me: When my foot slippeth, they magnify themselves against me." — Psalms 38:16 (ASV)

For I said, lest they rejoice over me. Here he also confirms his faith and his earnestness in prayer from this consideration: that if he should be forsaken by God, his enemies would triumph. This indignity on their part is of no small weight in inducing God to help us. For the wicked, in thus magnifying themselves against us and indulging in derision, not only make war against our flesh but also directly assail our faith and endeavor to destroy whatever religion and fear of God is in our hearts.

What is the object of all their mockery but to persuade us that what God has promised is vain and worthless? The Psalmist immediately adds that it is not without cause he is struck with the fear that his enemies would rejoice over him, since he had already experienced their proud boastings.

We are taught from this passage that the more our enemies increase in insolence and cruelty towards us, or the more they—seeing us already overwhelmed by a heavy load of adversities—in their proud disdain trample us under their feet, the more we ought to cherish the hope that God will come to our help.