Titus 1:15
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. 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.
The verse divides people into two classes by the state of the mind, heart and conscience: to the pure all things are pure, but to the defiled and unbelieving nothing is pure because even their mind and conscience is defiled. For those pure in heart, the duties and lawful pursuits of life are pure, but for those whose heart and conscience are defiled, everything is impure. Allowing impure thoughts to remain in the mind stains and debases the soul and weakens mental and physical powers.
Habits of intemperance injure mind and body and defile the mind and conscience, leaving a person unable to discern spiritual things and without clear discernment between right and wrong. The mind becomes confused so temptation is readily yielded to, and the defiled person passes into the power of Satan to be led away from God by deceptive temptation. Beholding and dwelling upon things pure and clean and lovely changes a person into Christlikeness, and keeping the mind fresh, clean and uplifted requires a persevering course of training to attract it to these things.
Even where duty requires beholding impure and defiling things, as in city mission work bearing God's message among the lower classes, one who carries Christlikeness in mind and remembers he is doing service to God remains pure, with Christ by his side and angels round about him wherever he goes. He does not fix on disgusting scenes and filthiness but watches and studies ways of saving souls from ruin and relieving wretchedness. Through Christlike love and pity he presents things high and holy and restores the moral image of God in man as man cooperates with God, a work those in danger to their souls must shrink from.
The verse rebukes those who profess to be Christians and have a knowledge of the truth but fail to bring it into the inner sanctuary of the soul to be sanctified through it, who in spirit conform to the world and its customs, maxims and influence instead of living the divine life opposed to the world. Their selfish earthly ambition for place and position and money-getting brings religion down to a low common level. It calls them to depart from all iniquity and dishonesty, come out from the world, put on the Lord Jesus Christ and make no provision for the flesh to fulfill its lusts at whatever cost in order to inherit eternal life.
The verse is given as a sharp rebuke that they may be sound in the faith and not give heed to Jewish fables and commandments of men that turn from the truth. Professing to know and serve God while denying Him in works leaves one abominable and disobedient and reprobate to every good work. The defiled and unbelieving condition describes unruly and vain talkers and deceivers whose mouths must be stopped, who bring serious charges against faithful ministers out of spiritual blindness and humiliation. Faithful ministers must not shun the unpleasant duty of reproving and rebuking them sharply that they may be sound in the faith.