The lesson begins with what the slides call the shortsighted view of man about justice: the habit of reducing justice to a purely human, horizontal matter, so that it becomes whatever courts decide, cultures affirm or ideologies demand. When justice is cut off from God it loses its stability, it offers false hope, it erases our accountability to Him, and it sets mercy and justice against each other.
Against this the study sets God as the essence and source of justice. Justice is not a standard above God that He obeys; it is what He is, the expression of His holy character, as the Judge of all the earth who does what is right. Because it is a communicable attribute, people made in His image carry a real but partial sense of justice, and the redeemed are being conformed to His just character through sanctification.
The third part turns to justice and mercy, which the secular world often treats as incompatible. In God's character they meet together; His mercy is never unjust and His justice is never unmerciful. Justice without mercy becomes harsh and leaves no room for repentance, and mercy without justice becomes sentimental and leaves victims unprotected. The Lord who is compassionate and gracious will by no means clear the guilty, and both meet perfectly at the cross, where Christ bore the justice of God against sin so that mercy could reach sinners.