Romans 3:28

For we maintain that a man is justified by faith apart from observing the law.

(v28, NIV)

So boasting is done away with by faith. This is because we are justified by faith. Justification by faith happens separate from the observance of the law. There is no boasting and it cannot come from when any are justified. We can't look at others and laugh at them, boasting in our justification. It doesn't work that way because we didn't do anything to earn or merit our justification. It just doesn't work that way and it's important that we do not boast in anything of ourselves in any way. Boasting is excluded and justification is by faith apart from the law.