arrogant about one’s own goodness and moral virtue
—She thinks she’s so much better than everyone else. I can’t stand her holier-than-thou attitude
In the Bible, holy means “to be sacred, worthy of worship, or, in the case of people, in harmony with God’s will.” But Isaiah reported God’s criticism of people who claimed to be holy while breaking his laws. In fact, they were so arrogant that when other people approached them, they told them to stay away:
Keep to yourself!
Don’t get near me, for I am holier than you [holier than thou]! (Isaiah 65:5)