John Calvin Commentary Psalms 118:27

"Jehovah is God, and he hath given us light: Bind the sacrifice with cords, even unto the horns of the altar." — Psalms 118:27 (ASV)

Jehovah is God. Here the prophet establishes what he said previously: that God, out of compassion for his Church, dispelled the darkness and introduced the light of his grace when David ascended the throne. For that event was the harbinger of the redemption which was expected to be accomplished in due time by Christ.

He also asserts that God was the author of that deliverance, so wonderful and unexpected, and he declares that, by the result, he clearly showed himself to be truly God. These words, Jehovah himself is a strong God, because he has restored the light of life to us, are implicitly emphatic.

For as the faithful, due to the confused state of the Church, were reduced almost to the brink of despair, the ungodly imagined that all this had happened to the children of Abraham because God himself had, as it were, forsaken them. Therefore, he returns to offer anew his thankful acknowledgments for the divine grace.

He commands the faithful to bind the victim to the horns of the altar, because, according to the legal institute, they could not offer solemn thanks to God without sacrifices. As David was a strict observer of the Law, he would not omit the ceremonial observances which God had commanded.

He would, however, always keep his attention steadily fixed on their grand design and would resort to them only as aids to help him in presenting a spiritual service to God. Now that the dispensation of shadows has passed away, it remains for us to offer to God our thanksgivings through Christ, who sanctifies them by his own immaculate offering, lest we should be prevented by the corruptions of our flesh from this exercise of godliness.

That David turned his attention to the praises of God is very clear from the following verse, in which he promises that he would celebrate the name of God, because he was his God, and he knew it; that is, he felt from experience that from his hand he could count on receiving sure and immediate assistance.