en_tn/psa/037/031.md

The law of his God is in his heart

Here "in his heart" refers to his deepest inner being. Alternate translation: "He treasures the commands of his God in his inner being" (See: rc://en/ta/man/jit/figs-metonymy)

his feet will not slip

Here failure to obey Yahweh is spoken of as slipping off a safe path and falling. Alternate translation: "he will walk safely in the way God wants him to walk" or "he will safely do the things God wants him to do" (See: rc://en/ta/man/jit/figs-metaphor)