New Revised Standard Version
To the pure all things are pure, but to the corrupt and unbelieving nothing is pure. Their very minds and consciences are corrupted.

Contemporary English Version
Everything is pure for someone whose heart is pure. But nothing is pure for an unbeliever with a dirty mind. That person's mind and conscience are destroyed.

New American Bible
To the clean all things are clean, but to those who are defiled and unbelieving nothing is clean; in fact, both their minds and their consciences are tainted.

Douay-Rheims Bible
All things are clean to the clean: but to them that are defiled and to unbelievers, nothing is clean: but both their mind and their conscience are defiled.

All things are clean to the clean: but to them that are defiled and to unbelievers, nothing is clean: but both their mind and their conscience are defiled.

the pure.

Luke 11:39-41 And the Lord said to him: Now you, Pharisees, make clean the outside of the cup and of the platter: but your inside is full of rapine and iniquity. . . .

Acts 10:15 And the voice spoke to him again the second time: That which God hath cleansed, do not thou call common.

Romans 14:14,20 I know, and am confident in the Lord Jesus, that nothing is unclean of itself: but to him that esteemeth any thing to be unclean, to him it is unclean. . . .

1 Corinthians 6:12,13 All things are lawful to me: but all things are not expedient. All things are lawful to me: but I will not be brought under the power of any. . . .

1 Corinthians 10:23,25,31 All things are lawful for me: but all things do not edify. . . .

1 Timothy 4:3,4 Forbidding to marry, to abstain from meats, which God hath created to be received with thanksgiving by the faithful and by them that have known the truth. . . .

but.

Proverbs 21:4 Haughtiness of the eyes is the enlarging of the heart: the lamp of the wicked is sin.

Haggai 2:13 And Haggai said: If one that is unclean by occasion of a soul touch any of all these things, shall it be defiled? And the priests answered, and said: It shall be defiled.

Zechariah 7:5,6 Speak to all the people of the land, and to the priests, saying: When you fasted, and mourned in the fifth and the seventh month for these seventy years: did you keep a fast unto me? . . .

Matthew 15:18 But the things which proceed out of the mouth, come forth from the heart, and those things defile a man.

Romans 14:20,23 Destroy not the work of God for meat. All things indeed are clean: but it is evil for that man who eateth with offence. . . .

1 Corinthians 11:27-29 Therefore, whosoever shall eat this bread, or drink the chalice of the Lord unworthily, shall be guilty of the body and of the blood of the Lord. . . .

their.

1 Corinthians 8:7 But there is not knowledge in every one. For some until this present, with conscience of the idol, eat as a thing sacrificed to an idol: and their conscience, being weak, is defiled.

Hebrews 9:14 How much more shall the blood of Christ, who by the Holy Ghost offered himself unspotted unto God, cleanse our conscience from dead works, to serve the living God?

Hebrews 10:22 Let us draw near with a true heart, in fulness of faith, having our hearts sprinkled from an evil conscience and our bodies washed with clean water.