The LORD shall reign for ever and ever.

Wesley's Notes

15:18 The Lord shall reign for ever and ever - They had now seen an end of Pharaoh's reign, but time itself shall not put a period to Jehovah's reign, which like himself is eternal.

Matthew Henry's Concise Commentary

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.