Albert Barnes Commentary Isaiah 57:18

"I have seen his ways, and will heal him: I will lead him also, and restore comforts unto him and to his mourners." — Isaiah 57:18 (ASV)

I have seen his ways - That is, either his ways of sin or of repentance. Most probably, it means the former. The idea is that God had seen how prone His people were to sin, and that He would now interpose to correct their proneness to sin against Him and to remove from them the judgments that had been brought upon them as a consequence of their crimes.

And will heal him - That is, I will pardon and restore him. Sin, in the Scriptures, is often represented as a disease, and pardon and salvation as a healing of the disease (2 Chronicles 7:14; Psalms 41:4; Jeremiah 3:22; Jeremiah 17:4; Jeremiah 32:6; Hosea 14:4; see the notes at Isaiah 6:10).

And to his mourners - To the pious portion that mourned over their sin, or to the nation that would sigh in their long and painful captivity in Babylon.