Charles H. Spurgeon on Psalms 57:1

Soul. His soul trusted in God; and this is a form of expression the force of which is not to be overlooked; for it implies that the trust which he exercised proceeded from his very innermost affection —that it was of no volatile character, but deeply and strongly rooted. He declares the same truth in figurative terms, when he adds his persuasion that God would cover him with the shadow of his wings. John Calvin.