Psalms 31:3

3. For thou art my rock. This verse may be read as one sentence, thus: As thou art like a tower for my defense, for thy name’s sake direct and guide me during my whole life. And thus the conjunction, as in many similar cases, would be superfluous. But I rather prefer a different sense, namely, that David, by interjecting this reflection, encourages himself not only to earnestness in prayer, but also in the confident hope of obtaining his requests. We know, at all events, that it is usual with him to mingle such things in his prayers as may serve to remove his doubts, and to confirm his assurance. Having, therefore, expressed his need, he assures himself, in order to encourage and animate himself, that his prayer shall certainly have a happy answer. He had formerly said, Be thou my strong rock and fortress; and now he adds, Assuredly thou art my rock, and my fortress: intimating, that he did not throw out these words rashly, like unbelievers, who, although they are accustomed to ask much from God, are kept in suspense by the dread of uncertain events. From this he also draws another encouragement, that he shall have God for his guide and governor during the whole course of his life. He uses two words, lead and guide, to express the same thing, and this he does (at least so I explain it) on account of the various accidents and unequal vicissitudes by which the lives of men are tried: as if he had said, Whether I must climb the steep mountain, or struggle along through rough places, or walk among thorns, I trust that thou wilt be my continual guide. Moreover, as men will always find in themselves matter for doubt, if they look to their own merits, “Si los hommes regardent a leur dignite.” — Fr.