What does the Bible say about conceit / being conceited?

Pride. There are several words so translated in the Greek Testament. The one used here (hyperephania) conveys the sense of a spirit of self-exaltation in a man coupled with the disparagement of others. The Pharisees who trusted in themselves that they were righteous and despised others (Luke 18:9) are flagrant examples, but the Gentiles are not free from guilt in this respect any more than the Jews (Rom. 1:30). This arrogance displays itself in boastful words and vain-glorious deeds, but its origin is within the heart, as is shown by that sentence from the Magnificat: "He scattered the proud in the imagination of their heart" (Luke 1:51). This particular form of haughtiness is obnoxious to God and amenable to His summary judgment, for both James and Peter write that "God resists the proud, and gives grace to the humble" (James 4:6; 1 Peter 5:5).

"Let us not become vainglorious, challenging (or provoking) one another, envying one another." We usually call vainglory, conceit. The law makes us more vainglorious or conceited than we were before, instead of destroying our vainglory, because the law makes me think of myself. As we have seen, if we use the law in the right way it is most useful, for when I think of myself, and see how bad I am — when I see how far short of the righteous demands of the law I come — then the law helps to compel me to own myself a lost sinner. But the law, as we have seen, never can produce righteousness.

The meaning of the last clause, "Be not wise in your own conceit," is intimately connected with what has been already said. Still, every word of scripture has its own place, its meaning, its own application. Self-conceit, not infrequently, is the offspring of weakness and ignorance. The mind becomes inflated from a fancied superiority to those around us, the opinions of the lowly are disregarded, and self-confidence naturally follows. So far as this species of pride manifests itself among Christians, the prosperity of the church is destroyed, and the blessing of the individual effectually hindered. May the Lord give us the spirit of a little child, humble, docile, dependent. "Be not wise in thine own eyes," says the wise man fear the Lord and depart from evil. …" "Woe unto them that are wise in their own eyes," says the prophet, "and prudent in their own sight." Proverbs 3:7; Isaiah 5:21.

"Seest thou a man wise in his own conceit? there is more hope of a fool than of him" (Prov. 26:12); of all fools the conceited fool is the worst. Pride makes a man incapable of receiving counsel.

If we consider ourselves honestly in the presence and in the light of God, we will be poor in spirit, as human honour and greatness cannot continue to exist when He looks at us. Examples of such an attitude of mind are Abraham (Genesis 18:27), Job (Job 42:5-6), Isaiah (Isaiah 6:1-5), the publican in the temple (Luke 18:13) and Simon Peter (Luke 5:8). As long as we measure ourselves with ourselves or compare ourselves with other Christians, we will always find some reason for self-satisfaction. In the world and, sad to say, among Christians too, what mostly counts is outward success, high position and prestige. The consequence is arrogance, overestimation of one’s abilities and conceit. Only in the presence of God do we become and remain poor in spirit.

If we consider ourselves honestly in the presence and in the light of God, we will be poor in spirit, as human honour and greatness cannot continue to exist when He looks at us. Examples of such an attitude of mind are Abraham (Gen.18:27), Job (Job 42:5-6), Isaiah (Isa. 6:1-5), the publican in the temple (Luke 18:13) and Simon Peter (Luke 5:8). As long as we measure ourselves with ourselves or compare ourselves with other Christians, we will always find some reason for self-satisfaction. In the world and, sad to say, among Christians too, what mostly counts is outward success, high position and prestige. The consequence is arrogance, overestimation of one's abilities and conceit. Only in the presence of God do we become and remain poor in spirit.

Of all moral sins the Lord Jesus considered pride one of the worst and most hateful. There may be the pride of race, or the pride of face, or the pride of place, but the worst is the pride of grace. To have a superior attitude towards other Christians and pretend to be more spiritual than they, perhaps because of more light and understanding of the Scriptures. There is a danger in much knowledge, even in much Bible knowledge. The apostle Paul warns against this: “ … we know that we all have knowledge. Knowledge puffeth up, but love edifieth” (1 Cor. 8:1). Actually, proud persons are very miserable persons because no one loves them since they keep themselves so aloof. Never forget that pride was at the root of Satan's fall: “ … lest being lifted up with pride he fall into the condemnation of the devil” (1 Tim. 3:6).

Pride is in every human heart; it runs in man's blood; all are afflicted with this disease, though by too many, alas, it is regarded rather as an ornament than a blemish. The Word of God says simply of “a high look, and a proud heart,” so much thought of in the world, that they are sin (Prov.21:4). They are hateful to God (Prov.6:16,17; 16:5), and to Christ, typified by wisdom (Prov.8:13).

Pride on the other hand is most offensive to Jehovah, and dangerous, yea, destructive, to man; and he is apt to be most lifted up when the blow falls; as we may see throughout Scripture, a haughty spirit before a fall. So Nebuchadnezzar, where mercy interceded; so Haman, where was only judgment.

The actuating motive in this audacious act of king Uzziah's is not made known. It has been suggested that he wished, like the Egyptian kings, to combine in himself both the office of king and high priest, so arrogating to himself the religious as well as the civil power. But whatever the immediate impelling motive, we know the primary cause of his profane deed. It was pride, the really "original sin," that hideous parent-sin of all succeeding sins, whether among angels, or among men (1 Tim. 3:6; Ezek. 28:2, 17). "He was marvelously helped till he was strong. But when he was strong, his heart was lifted up to his destruction." "Strength of Jehovah" was the meaning of his name; and happy would it have been for him had he realized that only in His strength is any really strong. "My strength," says He who is "the Almighty" (Rev. 1:8), "is made perfect in weakness." "When I am weak, then am I strong," wrote one who knew his own utter powerlessness and his Lord's sufficient strength. "Be strong in the Lord," he cautions his fellow-weaklings. Uzziah prospered; and because of his prosperity, his foolish heart was lifted up with pride: and in him was fulfilled his great ancestor's proverb, "The prosperity of fools shall destroy them": and another — "Pride goeth before destruction, and a haughty spirit before a fall" (Prov. 1:32; 16:18).