Charles Ellicott Commentary Isaiah 55:3

"Incline your ear, and come unto me; hear, and your soul shall live: and I will make an everlasting covenant with you, even the sure mercies of David." — Isaiah 55:3 (ASV)

Your soul shall live ... —Better, revive. The idea is that of waking to a new life.

I will make an everlasting covenant ... —These words find their explanation in the “new covenant” of Jeremiah 31:31 and Luke 22:20, but what follows shows that it is understood as the expansion and completion of the covenant that had been made with David (2 Samuel 7:12–17; Psalms 89:34–35), as the representative of the true King, whom Isaiah now contemplates as identical with the “servant of the Lord.” For “sure mercies,” understand the unfailing loving-kindnesses, which were “of David,” as given to him and his seed by Jehovah.