1)  Isa. 64:5-7 - ⁵You come to the help of those who gladly do right, who remember your ways. But when we continued to sin against them, you were angry. How then can we be saved? ⁶All of us have become like one who is unclean, and all our righteous acts are like filthy rags; we all shrivel up like a leaf, and like the wind our sins sweep us away. ⁷No one calls on your name or strives to lay hold of you; for you have hidden your face from us and made us waste away because of our sins.

Many people take the statement "our righteous acts are like filthy rags" and distort it into the idea that God sees even the righteous acts of Christians as "filthy rags."  They use this belief to justify sin, claiming that obeying God is not important because "our righteous acts are like filthy rags to God anyway."  Some people even use this verse to make the claim that Christians sin just as much as the rest of the world, and the only difference is that Christians are forgiven for their sins because they are "covered in the blood of Christ."  The problem is that these beliefs clearly contradict the rest of the Bible, and this part of the verse is taken entirely out of context.  In the book of Isaiah, Isaiah the prophet describes repeatedly how Israel has become corrupt and has turned away from God.  In chapter 64, verse 6, Isaiah says "All of us have become like one who is unclean, and all our righteous acts are like filthy rags. . ."  He is describing how bad Israel has become, that even the good they are trying to do is "like filthy rags."  Think about people who try to do good deeds but have selfish or impure motives.  For example, people who give to charities to feel good or enhance their reputation, or people who flatter others for their own benefit.  These people may think and feel like they are doing good deeds, but God knows that their motives are selfish and ungodly.