Isaiah 63:13

“That led them through the deep, &c.] The depths, the bottom of the sea; not through the shallow, but where the waters had been deepest, the descent greatest; and at the bottom of which might have been expected much filth and dirt to hinder them in their passage, yet through this he led them: as an horse in the wilderness; or rather, “in a plain”, as the wordf1236 sometimes signifies; and so Kimchi renders it a plain land, and Jarchi smooth land. The sense is, that the Israelites passed through the sea with as much ease, and as little difficulty, as a good horse will run over a plain, where there is nothing to stop his course: that they should not stumble? there being no clay to stick in, no…”

“deep--literally, "the tossing and roaring sea." wilderness--rather, the "open plain" [HORSLEY], wherein there is no obstacle to cause a horse in its course the danger of stumbling.”

“That led them through the deep - They went through the deep on dry land - the waters having divided and left an unobstructed path. As an horse in the wilderness - As an horse, or a courser, goes through a desert without stumbling. This is a most beautiful image. The reference is to vast level plains like those in Arabia, where there are no stones, no trees, no gullies, no obstacles, and where a fleet courser bounds over the plain without any danger of stumbling. So the Israelites were led on their way without falling. All obstacles were removed, and they were led along as if over a vast smooth plain. Our word ‘wilderness,’ by no means expresses the idea here. We apply it to uncultivated…”

“As an horse - With as much ease and tenderness, as an horse led by the bridle. Not stumble - That, tho' the sea were but newly divided, yet it was dried and smoothed by the wind, that God sent, as it were to prepare the way before them. Isaiah 63:14”

“Psa 106:9; Hab 3:15 Isaiah 63:14”