[Jesus' blood shows God's] righteousness at the present time, so that he might be just and the justifier of the one who has faith in Jesus.
Romans 3:26

By declining to punish sin in the here and now when he is within his rights, he demonstrates his righteousness and the ultimate justice of his judgment. When he finally judges mankind, no one will have an excuse, because he gave us ample time to repent or to prove our sinfulness. He is just because he establishes the Law and the guilt of lawbreakers, but he justifies those who have faith in Yeshua by setting aside their guilt.

“His righteousness” is dikaiosune, which is the same root as justify. Everywhere the English says “justify” in the New Testament, read it as “made/declared righteous”.