Albert Barnes 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 depart - (See the notes at Isaiah 51:6).

The covenant of my peace - That is, the covenant by which I promise peace and prosperity to you.