Titus 1:15

All things, are pure, unto the pure, but, unto the polluted and faithless, nothing, is pure, but polluted are both their mind and conscience;

Romans 14:20

Do not, for the sake of food, be throwing down the work of God! All things, indeed, are pure; but, ill, is it for the man who with occasion of stumbling doth eat, -

Romans 14:23

But, he that is in doubt, if he eat, hath condemned himself, - because, it was not of faith, and, everything which is not of faith, is sin.

Romans 14:14

I know and am persuaded in the Lord Jesus - that, nothing, is profane of itself, - save to him who reckoneth anything to be profane, unto that man, it is profane,

Matthew 15:18

while, the things which proceed out of the mouth, out of the heart, come forth, and, they, defile the man.

Acts 10:15

And a voice came again, a second time, unto him - What things, God, hath cleansed, be not, thou, making common.

Proverbs 21:4

Loftiness of eyes, and ambition of heart - the lamp of the lawless, are sin.

Haggai 2:13

Then said Haggai, If one who is defiled for a dead person touch any of these, shall it be defiled? And the priests answered and said, It shall be defiled.

Zechariah 7:5-6

Speak thou unto all the people of the land, and unto the priests, saying, - When ye fasted and lamented in the fifth and in the seventh, even these seventy years, did ye, really fast, unto, me?

Luke 11:39-41

And the Lord said unto him: Now, ye, the Pharisees, the outside of the cup and of the tray, do make pure; but, your inward part, is full of plunder and wickedness.

1 Corinthians 6:12-13

All things, unto me, are allowable, but, not all things, are profitable: all things, unto me, are allowable, but, I, will not be brought under authority by any.

1 Corinthians 8:7

Howbeit, not in all, is the knowledge; but, some, by their familiarity, until even now, with the idol, as an idol-sacrifice, eat it, and, their conscience, being, weak, is defiled.

1 Corinthians 10:23

All things are allowable - but, not all things, are profitable, - all things are allowable - but, not all things, upbuild.

1 Corinthians 10:25

Whatsoever, in the market, is sold, eat, - asking no question, for conscience sake;

1 Corinthians 10:31

Whether, therefore, ye eat or drink, or whatsoever ye do, do, all things to the glory of God.

1 Corinthians 11:27-29

So that, whosoever may be eating the loaf, or drinking the cup of the Lord, in an unworthy manner, shall be responsible for the body and blood of the Lord.

1 Timothy 4:3-4

Forbidding to marry, commanding to abstain from foods which, God, created to be received with thanksgiving by them who believe and personally know the truth;

1 Timothy 6:5

incessant quarrellings of men wholly corrupt in their mind and bereft of the truth, - supposing godliness to be, a means of gain!

Hebrews 9:14

How much rather shall the blood of the Christ, who through an age-abiding spirit offered himself unspotted unto God, purify our conscience from dead works, to the rendering of divine-service, unto a Living God?

Hebrews 10:22

Let us approach with a genuine heart, in full assurance of faith, having been sprinkled, as to our hearts, from an evil conscience, and bathed, as to our bodies, 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
And the Lord said unto him: Now, ye, the Pharisees, the outside of the cup and of the tray, do make pure; but, your inward part, is full of plunder and wickedness.
Acts 10:15
And a voice came again, a second time, unto him - What things, God, hath cleansed, be not, thou, making common.
Romans 14:14
I know and am persuaded in the Lord Jesus - that, nothing, is profane of itself, - save to him who reckoneth anything to be profane, unto that man, it is profane,
1 Corinthians 6:12
All things, unto me, are allowable, but, not all things, are profitable: all things, unto me, are allowable, but, I, will not be brought under authority by any.
1 Corinthians 10:23
All things are allowable - but, not all things, are profitable, - all things are allowable - but, not all things, upbuild.
1 Timothy 4:3
Forbidding to marry, commanding to abstain from foods which, God, created to be received with thanksgiving by them who believe and personally know the truth;

Their

1 Corinthians 8:7
Howbeit, not in all, is the knowledge; but, some, by their familiarity, until even now, with the idol, as an idol-sacrifice, eat it, and, their conscience, being, weak, is defiled.
Hebrews 9:14
How much rather shall the blood of the Christ, who through an age-abiding spirit offered himself unspotted unto God, purify our conscience from dead works, to the rendering of divine-service, unto a Living God?
Hebrews 10:22
Let us approach with a genuine heart, in full assurance of faith, having been sprinkled, as to our hearts, from an evil conscience, and bathed, as to our bodies, with pure water;

General references

Leviticus 7:19
And, the flesh that toucheth anything unclean, shall not be eaten, in fire, shall it be consumed, - but, as for the other flesh, any one who is clean, may eat flesh.
Leviticus 10:10
That ye may make a difference, between the sacred and the common, - and between the unclean and the clean;
Leviticus 11:34
Of all the food that may be eaten, that whereon shall come water, shall be unclean, - and, all drink which might be drunk in any such vessel, shall he unclean.
Deuteronomy 14:3
Thou shalt not eat any abominable thing.
Acts 24:16
herein, even I, myself, am studying to have, an unoffending conscience, towards God and men, continually.