“Holier than thou” is a phrase used to describe someone who acts superior to others or is perceived to act that way. Typically, the phrase refers to an attitude that places an individual above others on a moralistic level. Although no one is perfect, this outlook might lead a person to be quick to point out other people's flaws but rarely notice his or her own. The term often refers to someone so pious and devout in his beliefs that he judges others, which many people consider to be exactly the opposite of the biblical warning “judge not lest ye be judged.”
The exact origin of this phrase is unknown. It is sometimes presumed to have originated from a biblical passage in Isaiah 65:5, the King James Version translation of which states: “come not near me, for I am holier than thou.” Regardless of its origin, the phrase didn't come into common usage in the English language until the 20th century.
The word “thou” originates from Old English. Although is used as an ordinary pronoun meaning “you,” it was once used in certain Bible translations to refer exclusively to God and was capitalized. When considered in light of this knowledge, the phrase “holier than thou” might be interpreted to mean putting oneself above God.
The attitude of the biblical Pharisees, a group of religious leaders who were very devout in their beliefs, might be interpreted as “holier than thou.” According to the books of the New Testament, the Pharisees adhered so strictly to religious laws that they opposed Jesus doing good works on the sabbath. In so doing, their attitude was said to have been a transgression of the law because in their self-righteousness, they placed themselves above God.