God has given us a new heart and a new Spirit, the Spirit of Jesus into us. So our heart should be "perfect". God commanded us to renew our mind (Romans 12:2), not to change our hearts, because we cannot do ourselves, God can by His Grace. But verses in NT like these: Matthew 15:19 or in OT Jeremiah 17:9 indicated otherwise. Moreover, many ministers still exhorted us to check our hearts. I am confused in the difference between heart and mind - which were in our hands. Thank you very much.
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The mind is the intellect and the heart are feelings and emotions.