23:2-3a: - he leads me beside quiet waters,
he restores my soul.

Though separated by the versification in our Bible, these two lines should probably be read together, hendiadys-like, as reinforcing one another. Or "he restores my soul" may be understood as the conclusive climax of being made to lie down in green pastures and being led beside quiet waters.

NIV's "quiet waters" is, literally, "restful waters." The picture is "most likely a gently flowing stream or a placid pool which makes for easy drinking, though it could also mean 'waters where I may rest'."1

Water appears as an important imagery in the poetic literature of the OT. In Psm 1, e.g., the righteous person is compared to a tree "planted by streams of water." In particular the picture of being led beside "quiet" or "restful" waters here should probably be understood against the contrasting images of the "deep waters," the "raging waters," or the "mighty waters," metaphors for the chaos of life that overwhelm, debilitate and confuse, situations from which the soul needs to be restored, found elsewhere in the Psalter:

He reached down from on high and took hold of me; he drew me out of deep waters. (Psm 18:6)

Therefore let everyone who is godly pray to you while you may be found; surely when the mighty waters rise, they will not reach him. (Psm 32:6)

God is our refuge and strength, an ever-present help in trouble. Therefore we will not fear, though the earth give way and the mountains fall into the heart of the sea, though its waters roar and foam and the mountains quake with their surging. (Psm 46:1-3)

Save me, O God, for the waters have come up to my neck. I sink in the miry depths, where there is no foothold. I have come into the deep waters; the floods engulf me. I am worn out calling for help; my throat is parched. My eyes fail, looking for my God. (Psm 69:1-3)

But I pray to you, O Lord, in the time of your favor; in your great love, O God, answer me with your sure salvation. 14 Rescue me from the mire, do not let me sink; deliver me from those who hate me, from the deep waters. 15 Do not let the floodwaters engulf me or the depths swallow me up or the pit close its mouth over me. (Psm 69:13-15)

If the Lord had not been on our side—let Israel say—if the Lord had not been on our side when men attacked us, when their anger flared against us, they would have swallowed us alive; the flood would have engulfed us, the torrent would have swept over us, the raging waters would have swept us away. (Psm 124:1-5)

Reach down your hand from on high; deliver me and rescue me from the mighty waters, from the hands of foreigners whose mouths are full of lies, whose right hands are deceitful. (Psm 144:7-8)

One of the recurring image of the shepherd in the Bible is of him seeking out the sheep that had gone astray and bringing it back to the fold. It is easy to imagine a sheep here that had gone astray, finding itself disoriented, lost, and overwhelmed, but is now found and brought back into the green pasture and quiet waters; that would have been the model picture of the soul restored.