מלכים ב כד:ד פירוש: רלב״ג

and the LORD would not pardon: This means that even though Menasseh repented, God was not willing to forgive his spilling of innocent blood. And it would seem that this included servants of the Lord - that he killed Isaiah son of Amoz because of how he reproached him. And thus our teachers of blessed memory said that Menasseh killed Isaiah.