Self-righteousness can mean two things that often go hand in hand: self-righteousness can mean seeking to save yourself through works, and self-righteousness can be a certainty that you are morally superior to others. People often think that righteousness is measured by what we do or what values we hold. For example, if someone obeys the law and lives a morally pure life, he is considered righteous. The Bible, however, tells us that since people are sinful by nature, we cannot earn our own righteousness (Romans 3:10, 20, 23). God hates self-righteousness because it is a lie. Self-righteousness drives people to pride rather than to love, and ultimately, self-righteousness separates us from God. For this reason we must continually humble ourselves before God and rest in the assurance of His grace.
Even people who have been saved by grace, and sometimes especially those people, feel morally superior because of the ways Christ has changed them, or the things they stopped doing because of Christ's work in their heart. Jesus tells a parable about a religious leader and a sinner that perfectly demonstrates what this self-righteousness looks like: "He also told this parable to some who trusted in themselves that they were righteous, and treated others with contempt: 'Two men went up into the temple to pray, one a Pharisee and the other a tax collector. The Pharisee, standing by himself, prayed thus: "God, I thank you that I am not like other men, extortioners, unjust, adulterers, or even like this tax collector. I fast twice a week; I give tithes of all that I get." But the tax collector, standing far off, would not even lift up his eyes to heaven, but beat his breast, saying, "God be merciful to me, a sinner!" I tell you, this man went down to his house justified, rather than the other. For everyone who exalts himself will be humbled, but the one who humbles himself will be exalted'" (Luke 18:9–14). This attitude of self-righteousness is dangerous and deceitful. It leads to pride, which leads to destruction (Proverbs 16:18). Therefore we must always humble ourselves before God, realizing that it was only by His grace that we are saved, and not by our own works, and that it is ultimately God who transforms our hearts and lives (Philippians 2:12–13).