Matthew 12:34-35

You brood of vipers! how can you, evil as you are, say anything good? For what fills the heart will rise to the lips.

Luke 6:45

A good man, from the good stores of his heart, brings out what is good; while a bad man, from his bad stores, brings out what is bad. For what fills a man's heart will rise to his lips.

Matthew 15:19

For out of the heart proceed evil thoughts--murder, adultery, unchastity, theft, perjury, slander.

Mark 7:21-23

For it is from within, out of the hearts of men, that there come evil thoughts--unchastity, theft, murder, adultery,

Mark 14:38

Watch and pray," he said to them all, "that you may not fall into temptation. True, the spirit is eager, but human nature is weak."

Hebrews 12:15

Take care that no one fails to use the loving help of God, 'that no bitterness is allowed to take root and spring up, and cause trouble,' and so poison the whole community.

James 1:14-15

A man is in every case tempted by his own passions--allured and enticed by them.

Treasury of Scripture Knowledge

Summary

Keep thy heart with all diligence; for out of it are the issues of life.

Bible References

Keep

Mark 14:38
Watch and pray," he said to them all, "that you may not fall into temptation. True, the spirit is eager, but human nature is weak."
Hebrews 12:15
Take care that no one fails to use the loving help of God, 'that no bitterness is allowed to take root and spring up, and cause trouble,' and so poison the whole community.

For

Matthew 12:35
A good man, from his good stores, produces good things; while an evil man, from his evil stores, produces evil things.
Matthew 15:19
For out of the heart proceed evil thoughts--murder, adultery, unchastity, theft, perjury, slander.
Mark 7:21
For it is from within, out of the hearts of men, that there come evil thoughts--unchastity, theft, murder, adultery,
James 1:14
A man is in every case tempted by his own passions--allured and enticed by them.