God saw their works, that they turned from their evil way. God repented of the evil which he said he would do to them, and he didn't do it.
"And God saw their works ..." It is most significant that the sparing of Nineveh was altogether contingent upon their good works, and this in no sense meant that they had earned any respite from the punishment which was justly due them; and God's sparing them was an act of grace, despite the fact that if they had not repented and turned he would never have blessed them.  "It was not until the repentance of Nineveh was manifested through works that their salvation was effected by God."[38]  This is a plain doctrine of both the Old Testament and the New Testament, and it is opposed in every way to the popular misconception which alleges that people are saved "through faith alone."