In Psalm 23 many people equate His rod with discipline. This doesn’t fit the context of the Psalm. Would He make them lie down in green pastures and lead them beside quiet waters and then beat them with a rod?

Verse 4 says: “Even though I walk through the darkest valley, I fear no evil; for you are with me; your rod and your staff—they comfort me.” (NRSV) A rod of discipline wouldn’t make sense in this context.

God does discipline us as Hebrews 12:5-11 describes. But verse 11 says “Now, discipline always seems painful rather than pleasant at the time,”. When we are in the darkest valley, our Shepherd upholds us and comforts us.

Here are a collection of quotes from commentators.

William Barclay from Jesus As They Saw Him:

He [the shepherd] had his rod and his staff. The staff was a long crooked stick. Always the shepherd walked with it in his hand, and, when a sheep showed signs of straying, he would stretch out and pull it back with the crook. He carried the rod at his belt. It was a stout piece of wood, perhaps three feet long, with a lump of wood the size of an orange at one end of it. With this the shepherd fought the battles of the flock, using it to drive off wild beasts and to defend the flock against the robbers who would steal the sheep.

John Gill:

thy rod and thy staff they comfort me; not the rod of afflictions and chastisements, which is the sense of some Jewish as well as Christian interpreters; though these are in love, and the saints have often much consolation under them; but these are designed by the valley of the shadow of death, and cannot have a place here, but rather the rod of the word, called the rod of Christ’s strength, and the staff of the promises and the provisions of God’s house, the whole staff and stay of bread and water, which are sure unto the saints, and refresh and comfort them. The Targum interprets the rod and staff of the word and law of God; and those interpreters who explain the rod of afflictions, yet by the staff understand the law; and Jarchi expounds it, of the mercy of God in the remission of sin, in which the psalmist trusted: the allusion is to the shepherd’s crook or staff, as in other places; see Micah 7:14; which was made use of for the telling and numbering of the sheep, Lev. 27:32; and it is no small comfort to the sheep of Christ that they have passed under his rod, who has told them, and that they are all numbered by him; not only their persons, but the very hairs of their head; and that they are under his care and protection: the shepherd with his rod, staff, or crook, directs the sheep where to go, pushes forward those that are behind, and fetches back those that go astray; as well as drives away dogs, wolves, bears, etc. that would make a prey of the flock; and of such use is the word of God, attended with the power of Christ and his Spirit; it points out the path of faith, truth, and holiness, the saints should walk in; it urges and stirs up those that are negligent to the discharge of their duty, and is the means of reclaiming backsliders, and of preserving the flock from the ravenous wolves of false teachers: in a word, the presence, power, and protection of Christ, in and by is Gospel and ordinances, are what are here intended, and which are the comfort and safety of his people, in the worst of times and cases.

Adam Clarke:

Thy rod and thy staff - שבטך shibtecha, thy scepter, rod, ensign of a tribe, staff of office; for so שבט shebet signifies in Scripture. And thy staff, ומשענתך umishantecha, thy prop or support. The former may signify the shepherd’s crook; the latter, some sort of rest or support, similar to our camp stool, which the shepherds might carry with them as an occasional seat, when the earth was too wet to be sat on with safety. With the rod or crook the shepherd could defend his sheep, and with it lay hold of their horns or legs to pull them out of thickets, boys, pits, or waters.We are not to suppose that by the rod correction is meant: there is no idea of this kind either in the text, or in the original word; nor has it this meaning in any part of Scripture. Besides, correction and chastisement do not comfort; they are not, at least for the present, joyous, but grievous; nor can any person look forward to them with comfort. They abuse the text who paraphrase rod correction, etc.

Thomas Tymme from The Treasury of David:

“For thou art with me; thy rod and thy staff they comfort me.” Is God’s “staff” waxen so weak, that we dare not now lean too much thereon, lest it should break? or is he now such a changeling, that he will not be with us in our trouble according to his promise? Will he not give us this “staff” to stay us by, and reach us his hand to hold us up, as he hath been wont to do? No doubt but that he will be most ready in all extremity to help, according to his promise. The Lord that created thee, O Jacob, and he that formed thee, O Israel, saith thus; Fear not, for I will defend thee,” etc. Isaiah 43.