John Calvin Commentary Isaiah 54:10

"For the mountains may depart, and the hills be removed; but my lovingkindness shall not depart from thee, neither shall my covenant of peace be removed, saith Jehovah that hath mercy on thee." — Isaiah 54:10 (ASV)

For the mountains shall indeed be moved. He confirms the former statement and declares that the whole world would sooner be turned upside down than His mercy would fail. It would be pointless to ask here how “the mountains shall be moved, or the hills shall shake,” because the comparison is drawn from those things that appear to be strongest and most deeply rooted, in order to show that the foundation of the Church is far more durable.

Mountains are very strong, and earthquakes do not happen as frequently in them as in plains. Therefore, the Lord declares that even if that vast and huge mass of mountains were moved, or the heavens were to fall, His covenant would still endure, and His mercy towards the Church would not fail.

In this sense it is said in the Psalm, The Lord shall reign, the world shall be established (Psalms 93:1). In another passage it is even said,

Though the heavens pass away, the Church of God shall remain unshaken (Psalms 102:26, 28).

My mercy. In the word “mercy,” it should be noted what the nature of the covenant’s foundation is, for we can have no friendship with God unless He has mercy on us and receives us by free grace.

The covenant of my peace. He calls it “the covenant of peace,” because the Lord offers to us all that belongs to perfect happiness, as the Hebrew writers also, under the word “peace,” include all posterity. Therefore, since this covenant contains solid and perfect happiness, it follows that all who are excluded from it are miserable.

Saith Jehovah, who hath compassion on thee. By saying that it is He “who hath compassion” on her, He again confirms what was said previously: that He will be reconciled in no other way, and for no other reason, than because He is compassionate and ready to pardon.