"God is not a man that he should lie, neither the son of man that he should repent. Hath he said and shall he not do it? Hath he spoken and shall he not make it good?" -- KJV "God is no mere human! He doesn't tell lies or change his mind. God always keeps his promises." (Numbers 23:19). -- CEV But here are some examples -- Isaiah 38:1-5 Jonah 3:10-4:2 -- After saying that he (God) would destroy Nineveh, he didn't because they repented. Exodus 32:9-14 -- Earlier God had intended to destroy the Israelites but did not when Moses interceded for them. ON THE OTHER HAND, God did not seem to respond to David's repentance (2 Samuel 12:13-23). And God told Jeremiah and Ezekiel that he would not even listen to requests of leniency for Judah (Jer. 7:16; 15:1; Ezek. 14:12-14).
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