John Calvin Commentary Psalms 18:32

"The God that girdeth me with strength, And maketh my way perfect?" — Psalms 18:32 (ASV)

It is God who has girded. This is a metaphor taken either from the belt or girdle of a warrior, or from the reins, in which Scripture sometimes places a man’s vigor or strength. It is, therefore, as if he had said, I, who would otherwise have been feeble and soft, have been made strong and courageous by the power of God.

He afterwards speaks of the success itself with which God had favored him; for it would not be enough for people to have prompt and active courage, nor even to excel in strength, if their undertakings were not at the same time crowned with a prosperous outcome. Irreligious men imagine that this proceeds from their own prudence, or from fortune; but David ascribes it to God alone: It is God who has made my way perfect. The word way is here to be understood as the course of our actions, and the language implies that whatever David undertook, God, by his blessing, directed it to a successful outcome.