Assurance is a subjective experience, an inner sureness resulting from the exercise of faith. Justification is a judicial decree or declaration of God. Since God cannot lie, and He does not change, this judicial decision makes our restoration to His favor an objective and eternal reality. Justification is the exact opposite of condemnation; it is God’s acquittal. The God who has declared the case decided in our favor on the basis of the merits of Christ to whom we are joined by faith and He will never again bring up the matter. For this reason justification gives us peace with God. 

Justification eliminates any legitimate source of condemnation. 

Who shall lay anything to the charge of God’s elect? It is God that justifieth. Who is he that condemneth? It is Christ that died, yea rather, that is risen again, who is even at the right hand of God. Who also maketh intercession for us (Romans 8:33, 34).  

 Justification changes our position in relation to God. 

God no longer looks upon us apart from our union with Christ. Since He sees us “in Him,” our acceptance is complete and final. There is therefore now no condemnation to them which are in Christ Jesus, who walk not after the flesh, but after the Spirit (Romans 8:1). To the praise of the glory of his grace, wherein he hath made us accepted in the beloved (Ephesians 1:6).  

 Justification includes forgiveness of sins on the basis of the penalty already paid by Christ.

God’s wrath has already been folly placated (propitiated), and His holiness perfectly satisfied through Christ’s self-sacrifice in payment for our sins (expiation). Christ declared that His work was finished; God continues to consider it finished.  

For God hath not appointed us to wrath, but to obtain salvation by our Lord Jesus Christ, Who died for us, that, whether we wake or sleep, we should live together with him (1 Thessalonians 5:9, 10).