Romans 3:26 (NKJV), “to demonstrate at the present time His righteousness, that He (God) might be just and the justifier of the one who has faith in Jesus.”
God is omniscient; He knows all things. He knows the future. Isaiah 46:10 (NIV), “I make known the end from the beginning, from ancient times, what is still to come.”
Before man was created, God knew Adam would sin. God planned to give man free-will. However, He also knew that because man would have no experience with sin, the first couple would fail to obey. Therefore, He also planned man’s redemption in advance. 1 Peter 1:18-20 (NIV), “For you know that it was not with perishable things such as silver or gold that you were redeemed…but with the precious blood of Christ, a lamb without blemish or defect. He was chosen before the creation of the world.”
Thus, we may understand how God is called the Justifier. It is by His plan that mankind is redeemed. Jesus is the instrument to fulfill God’s plan of salvation.
Rom. 3:22-26: “…all have sinned and come short of the glory of God. Being justified [cleared of guilt] freely by His grace through the redemption that is in Christ Jesus: Whom God [the Judge] hath set forth to be a propitiation [satisfaction] through faith in his blood. To declare His [the Judge’s] righteousness for in the remission of sins that are passed through the forbearance of God.” [Meaning, the Judge sent his Son and paid the claim against the condemned race, in order that He might set them at liberty without violating his own laws]. “To declare, I say, at this time His righteousness: that He might be JUST and [also] the justifier of [sinners] him which believe in Jesus”.
For a more detailed study, please download the free PDF: "God's Plan"