Titus 1:15

To the pure, all things are pure; but to those who are defiled and unbelieving, nothing is pure, but both their mind and their conscience are defiled.

Romans 14:20

Do not tear down the work of God for the sake of food All things indeed are clean, but they are evil for the man who eats and gives offense.

Romans 14:23

But he who doubts is condemned if he eats, because his eating is not from faith; and whatever is not from faith is sin.

Romans 14:14

I know and am convinced in the Lord Jesus that nothing is unclean in itself; but to him who thinks anything to be unclean, to him it is unclean.

Matthew 15:18

"But the things that proceed out of the mouth come from the heart, and those defile the man.

Acts 10:15

Again a voice came to him a second time, "What God has cleansed, no longer consider unholy."

Proverbs 21:4

Haughty eyes and a proud heart, The lamp of the wicked, is sin.

Haggai 2:13

Then Haggai said, "If one who is unclean from a corpse touches any of these, will the latter become unclean?" And the priests answered, "It will become unclean."

Zechariah 7:5-6

"Say to all the people of the land and to the priests, 'When you fasted and mourned in the fifth and seventh months these seventy years, was it actually for Me that you fasted?

Luke 11:39-41

But the Lord said to him, "Now you Pharisees clean the outside of the cup and of the platter; but inside of you, you are full of robbery and wickedness.

1 Corinthians 6:12-13

All things are lawful for me, but not all things are profitable. All things are lawful for me, but I will not be mastered by anything.

1 Corinthians 8:7

However not all men have this knowledge; but some, being accustomed to the idol until now, eat food as if it were sacrificed to an idol; and their conscience being weak is defiled.

1 Corinthians 10:23

All things are lawful, but not all things are profitable All things are lawful, but not all things edify.

1 Corinthians 10:25

Eat anything that is sold in the meat market without asking questions for conscience' sake;

1 Corinthians 10:31

Whether, then, you eat or drink or whatever you do, do all to the glory of God.

1 Corinthians 11:27-29

Therefore whoever eats the bread or drinks the cup of the Lord in an unworthy manner, shall be guilty of the body and the blood of the Lord.

1 Timothy 4:3-4

men who forbid marriage and advocate abstaining from foods which God has created to be gratefully shared in by those who believe and know the truth.

1 Timothy 6:5

and constant friction between men of depraved mind and deprived of the truth, who suppose that godliness is a means of gain.

Hebrews 9:14

how much more will the blood of Christ, who through the eternal Spirit offered Himself without blemish to God, cleanse your conscience from dead works to serve the living God?

Hebrews 10:22

let us draw near with a sincere heart in full assurance of faith, having our hearts sprinkled clean from an evil conscience and our bodies washed with pure water.

Treasury of Scripture Knowledge

Summary

Unto the pure all things are pure: but unto them that are defiled and unbelieving is nothing pure; but even their mind and conscience is defiled.

Bible References

The pure

Luke 11:39
But the Lord said to him, "Now you Pharisees clean the outside of the cup and of the platter; but inside of you, you are full of robbery and wickedness.
Acts 10:15
Again a voice came to him a second time, "What God has cleansed, no longer consider unholy."
Romans 14:14
I know and am convinced in the Lord Jesus that nothing is unclean in itself; but to him who thinks anything to be unclean, to him it is unclean.
1 Corinthians 6:12
All things are lawful for me, but not all things are profitable. All things are lawful for me, but I will not be mastered by anything.
1 Corinthians 10:23
All things are lawful, but not all things are profitable All things are lawful, but not all things edify.
1 Timothy 4:3
men who forbid marriage and advocate abstaining from foods which God has created to be gratefully shared in by those who believe and know the truth.

Their

1 Corinthians 8:7
However not all men have this knowledge; but some, being accustomed to the idol until now, eat food as if it were sacrificed to an idol; and their conscience being weak is defiled.
Hebrews 9:14
how much more will the blood of Christ, who through the eternal Spirit offered Himself without blemish to God, cleanse your conscience from dead works to serve the living God?
Hebrews 10:22
let us draw near with a sincere heart in full assurance of faith, having our hearts sprinkled clean from an evil conscience and our bodies washed with pure water.

General references

Leviticus 7:19
'Also the flesh that touches anything unclean shall not be eaten; it shall be burned with fire. As for other flesh, anyone who is clean may eat such flesh.
Leviticus 10:10
and so as to make a distinction between the holy and the profane, and between the unclean and the clean,
Leviticus 11:34
'Any of the food which may be eaten, on which water comes, shall become unclean, and any liquid which may be drunk in every vessel shall become unclean.
Deuteronomy 14:3
"You shall not eat any detestable thing.
Acts 24:16
"In view of this, I also do my best to maintain always a blameless conscience both before God and before men.