True believers, although they dwell safely under the protection of God, are, notwithstanding, exposed to many dangers, or rather they are liable to all the afflictions which befall mankind in common, that they may the better feel how much they need the protection of God.
David, therefore, here expressly declares, that if any adversity should befall him, he would lean upon the providence of God. Thus he does not promise himself continual pleasures; but he fortifies himself by the help of God courageously to endure the various calamities with which he might be visited.
Pursuing his metaphor, he compares the care which God takes in governing true believers to a shepherd’s staff and crook, declaring that he is satisfied with this as all-sufficient for the protection of his life. As a sheep, when it wanders up and down through a dark valley, is preserved safe from the attacks of wild beasts and from harm in other ways, by the presence of the shepherd alone, so David now declares that as often as he shall be exposed to any danger, he will have sufficient defence and protection in being under the pastoral care of God.
We thus see how, in his prosperity, he never forgot that he was a man, but even then seasonably meditated on the adversities which afterwards might come upon him. And certainly, the reason why we are so terrified, when it pleases God to exercise us with the cross, is, because every man, that he may sleep soundly and undisturbed, wraps himself up in carnal security.
But there is a great difference between this sleep of stupidity and the repose which faith produces. Since God tries faith by adversity, it follows that no one truly confides in God, but he who is armed with invincible constancy for resisting all the fears with which he may be assailed.
Yet David did not mean to say that he was devoid of all fear, but only that he would surmount it so as to go without fear wherever his shepherd should lead him. This appears more clearly from the context. He says, in the first place, I will fear no evil; but immediately adding the reason of this, he openly acknowledges that he seeks a remedy against his fear in contemplating, and having his eyes fixed on, the staff of his shepherd: For thy staff and thy crook comfort me.
What need would he have had of that consolation, if he had not been disquieted and agitated with fear? It ought, therefore, to be kept in mind, that when David reflected on the adversities which might befall him, he became victorious over fear and temptations, in no other way than by casting himself on the protection of God.
This he had also stated before, although a little more obscurely, in these words, For thou art with me. This implies that he had been afflicted with fear. Had not this been the case, for what purpose could he desire the presence of God? Besides, it is not against the common and ordinary calamities of life only that he opposes the protection of God, but against those which distract and confound the minds of men with the darkness of death. For the Jewish grammarians think that צלמות, which we have translated the shadow of death, is a compound word, as if one should say deadly shade.
David here makes an allusion to the dark recesses or dens of wild beasts, to which when an individual approaches he is suddenly seized at his first entrance with an apprehension and fear of death. Now, since God, in the person of his only begotten Son, has exhibited himself to us as our shepherd, much more clearly than he did in old time to the fathers who lived under the Law, we do not render sufficient honour to his protecting care, if we do not lift our eyes to behold it, and keeping them fixed upon it, tread all fears and terrors under our feet.*
*Commentary on the Book of Psalms, vol. 1, 394–396.