Some three thousand years ago, and about one thousand years before Christ, the Psalmist said:
“If Thou, Lord, shouldest mark iniquities, O Lord who shall stand? But there is forgiveness with Thee…” (Psa. 130:3,4).
The Psalmist did not explain, however, upon what basis a just and holy God could forgive a guilty sinner. This was to be proclaimed one thousand years later by the Apostle Paul, himself once “a blasphemer, and a persecutor and injurious”; the “chief” of sinners, but forgiven and saved by the infinite grace of God (1 Tim. 1:13-15).
Preaching Christ at Antioch, in the province of Pisidia, Paul declared:
“Be it known unto you therefore, men and brethren, that THROUGH THIS MAN IS PREACHED UNTO YOU THE FORGIVENESS OF SINS, AND BY HIM ALL THAT BELIEVE ARE JUSTIFIED FROM ALL THINGS, FROM WHICH YE COULD NOT BE JUSTIFIED BY THE LAW OF MOSES” (Acts 13:38,39).
But even this does not fully answer our question, for we must still ask: On what basis does God forgive sins through “this Man”? The answer is: on the basis of His payment for our sins on Calvary’s cross. Thus the Apostle wrote to the Romans, explaining how we may be…
“…justified freely by His [God’s] grace, THROUGH THE REDEMPTION THAT IS IN CHRIST JESUS” (Rom. 3:24).
Now, thank God, through Christ’s finished work, there is not a sinner who needs to remain unforgiven. source