...by his knowledge shall the righteous one, my servant, make many to be accounted righteous, and he shall bear their iniquities.
It was to show his righteousness at the present time, so that he might be just and the justifier of the one who has faith in Jesus.
For I am not aware of anything against myself, but I am not thereby acquitted. It is the Lord who judges me.
And such were some of you. But you were washed, you were sanctified, you were justified in the name of the Lord Jesus Christ and by the Spirit of our God. (ESV)