'Heart' in the Bible

Thou shalt not hate thy brother in thy heart: thou shalt surely rebuke thy neighbor, and not bear sin because of him.

And as for them that are left of you, I will send a faintness into their heart in the lands of their enemies: and the sound of a driven leaf shall chase them; and they shall flee, as one fleeth from the sword; and they shall fall when none pursueth.

I also walked contrary unto them, and brought them into the land of their enemies: if then their uncircumcised heart be humbled, and they then accept of the punishment of their iniquity;