John Calvin Commentary Psalms 136:13

"To him that divided the Red Sea in sunder; For his lovingkindness [endureth] for ever;" — Psalms 136:13 (ASV)

Who divided the Red Sea. I have already (Psalms 106:7) spoken of the word סוף, suph, and have therefore not hesitated to render it the Red Sea. The Psalmist speaks of divisions in the plural number. This has led some Jewish authors to conjecture that there must have been more passages than one—an instance of their solemn trifling in things about which they know nothing, and of their method of corrupting the Scriptures entirely with their vain fancies.

We may well laugh at such fooleries, yet we are to hold them at the same time in detestation, for there can be no doubt that the Rabbinical writers were led to this by the devil, as an artful way of discrediting the Scriptures. Moses plainly and explicitly asserts that the heaps of waters stood up on both sides, from which we infer that the space between was one and undivided.

But as the people passed through in troops and not one by one—the pathway being so broad as to allow them to pass freely, men and women, with their families and cattle—the Psalmist very properly mentions divisions, with reference to the people who passed through. This circumstance greatly enhanced the mercy of God, in that they saw large depths or channels dried up, so that they had no difficulty advancing in troops abreast.

Another circumstance that confirmed or enhanced the mercy shown was that Pharaoh was shortly afterwards drowned. For the very different outcome proved that it could not be due to any hidden, merely natural cause that some should have perished while others passed over with entire safety. The distinction made provided a conspicuous display of God’s mercy in saving his people.

Much is included in the single expression that God was the leader of his people through the wilderness. It was only by a succession of miracles of various kinds that they could have been preserved for forty years in a parched wilderness, where they lacked all means of subsistence.

So, we are to understand that this expression encompasses the various proofs of divine goodness and power that Moses mentioned as having been graciously given: feeding his people with bread from heaven, making water to flow from the rock, protecting them under the cloud from the sun’s heat, giving them a sign of his presence in the pillar of fire, preserving their clothing intact, and shielding them and their little ones in their exile wanderings under tents of leaves, along with innumerable other instances of mercy that must occur to the reader.