John Gill

He rebuked the Red sea also, and it was dried up,.... By sending a strong east wind, which drove the waters back, and made the sea a dry land, Exo 14:21. So he led them through the depths; that is, the deep waters of the sea, which were cast up as an heap, and stood as a wall on each side, through which they passed. As through the wilderness; or rather, "as on a plain"; for a passage through a wilderness where no roads are, and many obstructions be, is not easy; and so it is manifestly to be understood in Isa 63:13, where Jarchi and Kimchi interpret it a plain and smooth ground, a champaign country; and so the word is used for a plain, in opposition to mountains, in Jer 9:10, and then the sense is, that God led them through the sea, being dried up, as if they were led through a plain and open country, where was nothing to obstruct their march; an emblem of baptism, Co1 10:1, and of the passage of the people of God through this world; See Gill on Psa 78:13.