As a stone - The warriors in chariots are always represented on the monuments with heavy coats of mail; the corslets of "chosen captains" consisted of plates of highly tempered bronze, with sleeves reaching nearly to the elbow, covering the whole body and the thighs nearly to the knee. The wearers must have sunk at once like a stone, or as we read in Exodus 5:10, like lumps of lead.

Exodus 15:5They are extinct - They are destroyed, as the wick of a lamp is quenched suddenly when immersed in water. This is a striking figure, to denote the suddenness with which it was done, and the completeness of their destruction. As a flame is entirely put out when plunged beneath the water, so the whole host of the Egyptians were suddenly and completely destroyed in the Red Sea. The sentiment in this verse is, that God has power over the nations to control them; that it is one of his characteristics to lead on the enemies of his people to destruction; and that they are suddenly destroyed, and their hopes, and joys, and triumphs put out forever. If it was so in regard to the Egyptians, it will be also in regard to all his foes. And if this took place in regard to a nation, it shall also in regard to individual sinners who oppose themselves to God.

How oft is the candle of time wicked put out?

And how oft cometh their destruction upon them?

continued...

The depths have covered them,.... The depths of the sea covered Pharaoh and his host, so as to be seen no more; and in like manner will mystical Babylon, or antichrist, be destroyed, and be no more found and seen; as likewise the sins of God's people, being cast into the depths of the sea, and covered with the blood of Christ, will be seen no more; when they are sought for, they shall not be found:

they sunk into the bottom as a stone; into the bottom of the sea, as a stone thrown into anybody of water sinks and rises not up again; this circumstance is observed by Nehemiah 9:11.

their persecutors thou threwest into the deep, as a stone into the mighty waters; and thus a stone like a millstone being taken by an angel and cast into the sea, is made an emblem of the irrecoverable ruin and destruction of Babylon, or antichrist, Revelation 18:21.

"Floods cover them (יכסימוּ, defectively written for יכסיוּ equals יכסּוּ, and the suffix מוּ for מו, only used here); they go down into the deep like stone," which never appears again.

The depths have covered them: they sank into the bottom as a stone.

15:1-21 This song is the most ancient we know of. It is a holy song, to the honour of God, to exalt his name, and celebrate his praise, and his only, not in the least to magnify any man. Holiness to the Lord is in every part of it. It may be considered as typical, and prophetical of the final destruction of the enemies of the church. Happy the people whose God is the Lord. They have work to do, temptations to grapple with, and afflictions to bear, and are weak in themselves; but his grace is their strength. They are often in sorrow, but in him they have comfort; he is their song. Sin, and death, and hell threaten them, but he is, and will be their salvation. The Lord is a God of almighty power, and woe to those that strive with their Maker! He is a God of matchless perfection; he is glorious in holiness; his holiness is his glory. His holiness appears in the hatred of sin, and his wrath against obstinate sinners. It appears in the deliverance of Israel, and his faithfulness to his own promise. He is fearful in praises; that which is matter of praise to the servants of God, is very dreadful to his enemies. He is doing wonders, things out of the common course of nature; wondrous to those in whose favour they are wrought, who are so unworthy, that they had no reason to expect them. There were wonders of power and wonders of grace; in both, God was to be humbly adored.