And I am Jehovah thy God. Again the Lord declares his power; for so great is the unbelief and sluggishness of men, that, although it is frequently declared, yet the very smallest temptation shews that they are not fully convinced of it. They quickly fall back upon themselves, when they are hard pressed by afflictions; and when they hear that anything is in the power of God, they do not think that it belongs to them. Who divide the sea. He does not speak in general terms, but brings forward the instance which he had often mentioned before; for, by once redeeming the fathers, he held out to posterity the hope of eternal salvation. Justly, therefore, does he exclaim that he is the same God who long ago "divided the sea;" and next he magnifies the miracle by saying that its roaring billows were stilled at his command. (Exodus 14:21.) We ought to know, therefore, that there are no raging billows which God cannot allay and calm in order to deliver his Church. "It is he who," by his power, "stills the sea and makes it calm," (Job 26:12,) though it rage furiously; and he likewise drives and swells its waves, when he thinks fit; though literally, as I have remarked, the Prophet alludes to the history of the deliverance from Egypt. [1] Jehovah of hosts. The Lord is adorned with this title, that we may know how extensive is his power; and he exhibits that power as often as he is pleased to render assistance to his Church.

Footnotes

1 - "A l'histoire de la deliverance d'Egypte."

But I am the Lord thy God - In order to show them that he was able to save them, God again refers to the fact that he had divided the sea, and delivered their fathers from bondage and oppression.
That divided the sea - The Red Sea. The Chaldee renders this, 'That rebuked the sea.' The Septuagint, Ὁ ταράσσων ho tarassōn - 'Who disturbs the sea.' or, who excites a tempest. Lowth renders it, 'Who stilleth at once the sea.' The Hebrew word is the same which occurs in Isaiah 51:4, where it is rendered, 'I will make my judgment to rest' (רגע râga‛). Probably the idea here is, that he restrains the raging of the sea as if by fear; that is, makes it tranquil or still by rebuking it. He had this power over all raging seas, and he had shown it in a special manner by his rebuking the Red Sea and making it rest, and causing a way to be made through it, when the children of Israel came out of Egypt.
The Lord of hosts is his name - (See the notes at Isaiah 1:9; compare the notes at Isaiah 42:8).

But I am the Lord thy God that divided the sea, whose waves roared,.... Referring to the dividing of the Red sea by a violent wind, at which time the waves of it doubtless roared till they were made to stand quietly, as a wall on the right and left, for the Israelites to pass through, as in Isaiah 51:10. Or this is to be understood of the power of God at any time in stilling and quieting the sea when it rages; which signification the word (s) here used has, as Aben Ezra observes; which power is expressed by a rebuke or reproof of it. And so the Targum,
"I am the Lord thy God, that rebuketh the sea:''
and in like manner the Syriac version; see Psalm 106:9 with which compare Matthew 8:26. Now he that can do, and oftentimes has done this, can rebuke, restrain, and still the fury of the oppressors, the rage of the persecutors, Rome Pagan or Papal, and deliver out of their hands, Psalm 65:7,
the Lord of hosts is his name: the Lord of armies in heaven and earth, and therefore is able to do these things in a natural, civil, and religious sense.
(s) "qui tranquillat" Gakater; "faciens quiescere", so some in Vitringa; and the word has the signification of rest and quietness in ver 4.

divided . . . sea--the Red Sea. The same Hebrew word as "make to rest" (Isaiah 51:4). Rather, "that terrify the sea," that is, restrain it by My rebuke, "when its waves roar" [GESENIUS]. The Hebrew favors MAURER, "that terrify the sea so that the waves roar." The sense favors GESENIUS (Jeremiah 5:22; Jeremiah 31:35), or English Version (Isaiah 51:9-10, which favors the special reference to the exodus from Egypt).