God did not abandon man after his fall into sin, but from the beginning promised him a Redeemer. (Gen. 3:15).  This Redeemer was to satisfy for man’s sin, and reopen to him the gates of Heaven.  The Prophets foretold the coming of the Redeemer, and many things about His life, death, and triumph.
The promised Redeemer is Jesus Christ the Son of God, Who was born in Bethlehem and was crucified on Mount Calvary. 
The Son of God became man to redeem us, that is, to suffer and die for our sins.   “Thou shalt call His name Jesus, for He shall save His people from their sins.” (Matt. 1:21).

By the sin of Adam and Eve:
       God was infinitely offended
       Sanctifying Grace was lost to man
       The gates of Heaven were closed.

By the merits of Jesus Christ, and especially by His death upon the Cross:
       The Justice of God was perfectly satisfied;
       Sanctifying Grace was restored to man; and
       The gates of Heaven were reopened.

The promised Redeemer not only satisfied for the sin of Adam and Eve, but also for the sins of the whole world.  “He is the propitiation for our sins; and not for ours only, but also for those of the whole world.”  (1 Jn. 2:2).
This satisfaction for the sin of Adam and Eve, and for the sins of the whole world, was given to God’s infinite Justice by a sacrifice of infinite value, which was offered by the infinite Son of God. 
By the Sacrifice of the Cross, Jesus Christ, the infinite Son of God, paid to the Heavenly Father man’s infinite debt of sin.  The sacrifice of the Cross is the sacrifice of the New Testament, perpetuated in the Holy Sacrifice of the Mass.  The Mass is the constant renewal of the Sacrifice of the Cross.  To offer sacrifice means to offer God a visible gift, whole and entire.
 

GRACE

The chief results of the Redemption are:
       The satisfaction of the Justice of God
       The reopening of Heaven
       The regaining of Grace.
“Being justified freely by His Grace, through the Redemption that is in Christ Jesus.” (Rom. 3:24).

Grace is an interior supernatural free gift, which God confers upon the soul, through the merits of Jesus Christ, for our salvation. 
The merits of Jesus are His life, works, sufferings, and death.

Grace is a supernatural free gift.
It is a supernatural gift, because God confers it upon us for our salvation.
It is a free gift, because He gives it to us without any claim on our part.
Since Grace is a free gift of God, He is free to give more and greater Graces to some than to others.
The Bible tells us that God gives all men sufficient Grace to be saved. 
“Who will have all men to be saved, and to come to the knowledge of the truth.” (1 Tim. 2:4).
Because we have a free will, we can co-operate with Grace or reject it.
Those who co-operate with Grace are like the man of the parable who received five talents and used them well.  To him the Lord said: “Well done, good and faithful servant, because thou hast been faithful over a few things, I will place thee over many things.” (Matt. 25:21).

Those who reject Grace are like the man of the parable who received one talent and did not use it.  Of him the Lord said: “Take ye away therefore the talent from him, and give it to him that hath ten talents.” (Matt. 25:28).