Matthew 12:34-35

Ye brood of vipers, how can ye, being evil, speak good things? For out of the abundance of the heart the mouth speaketh.

Luke 6:45

A good man, out of the good treasure of his heart, bringeth forth that which is good; and an evil man, out of the evil treasure of his heart, bringeth forth that which is evil; for of the abundance of the heart the mouth speaketh.

Matthew 15:19

For out of the heart proceed evil thoughts, murders, adulteries, fornications, thefts, false witness, railings.

Mark 7:21-23

For from within, out of the heart of man proceed evil thoughts, adulteries, fornications, murders,

Mark 14:38

Couldest thou not watch one hour? Watch and pray, lest ye enter into temptation; the spirit indeed is willing, but the flesh is weak.

Hebrews 12:15

Looking diligently, lest any one fall from the grace of God, lest any root of bitterness springing up trouble you, and thereby many be defiled: Lest there be any fornicator or profane person,

James 1:14-15

But every man is tempted, when he is drawn away by his own desire and inticed.

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
Couldest thou not watch one hour? Watch and pray, lest ye enter into temptation; the spirit indeed is willing, but the flesh is weak.
Hebrews 12:15
Looking diligently, lest any one fall from the grace of God, lest any root of bitterness springing up trouble you, and thereby many be defiled: Lest there be any fornicator or profane person,

For

Matthew 12:35
A good man out of the good treasure bringeth forth good things: and an evil man out of the evil treasure bringeth forth evil things.
Matthew 15:19
For out of the heart proceed evil thoughts, murders, adulteries, fornications, thefts, false witness, railings.
Mark 7:21
For from within, out of the heart of man proceed evil thoughts, adulteries, fornications, murders,
James 1:14
But every man is tempted, when he is drawn away by his own desire and inticed.