I have 3...
My soul is among lions: and I lie even among them that are set on fire, even the sons of men, whose teeth are spears and arrows, and their tongue a sharp sword.
- Psalm 57:4
And let none of you imagine evil in your hearts against his neighbor.
- Zechariah 8:17a
For out of the heart proceed evil thoughts, murders, adulteries, fornications, thefts, false witness, blasphemies.
- Matthew 15:19
These all sum up to one key point and that is that one sin will always lead to another. A good thing to remember before you tell that little white lie.
I like using these with my children to teach them about honesty and integrity.