'Heart' in the Bible

wherefore I was grieved with that generation, and said, Always do they go astray in heart, and these have not known My ways;

See, brethren, lest there shall be in any of you an evil heart of unbelief in the falling away from the living God,

for the reckoning of God is living, and working, and sharp above every two-edged sword, and piercing unto the dividing asunder both of soul and spirit, of joints also and marrow, and a discerner of thoughts and intents of the heart;

may we draw near with a true heart, in full assurance of faith, having the hearts sprinkled from an evil conscience, and having the body bathed with pure water;

with teachings manifold and strange be not carried about, for it is good that by grace the heart be confirmed, not with meats, in which they who were occupied were not profited;