Only the gospel of Christ fully knows the mystery of sin and the problem of sin and everything which hides within it. The prodigal son of the Gospel is the perfect example of the repentant sinner. The Gospel shows us that man, through his free will, can share his life with Earth and with Heaven, with Satan and with God, with paradise and with hell. Sin gradually strips man of everything divine in him, paralyzes his every divine inclination and desire, until it finally throws him into the bosom of Satan. And then man reaches the plight of grazing the swine of his master, the Devil. The swine are passions, which are always greedy and gluttonous. In such a life, the unfortunate man is nothing more than insane. In a shocking parable of the Gospel, the Lord says about the prodigal son, ‘he came to himself,’ (Luke 15:17) How did he come to himself? He came to himself through repentance. Through sin, man becomes mad, insane. Every sin, even the most seemingly insignificant one, is always an insanity of the soul. Through repentance, man comes to his senses becomes complete again, comes to himself. Then he cries out loud to God, runs to Him, and cries towards Heaven, ‘Father, I have sinned against Heaven, and in thy sight’ (Luke 15:21). And what is the heavenly Father doing? He is always infinitely merciful upon seeing His child in a state of repentance. He has compassion for him, runs, embraces him, and kisses him. He orders His heavenly hosts, the holy angels: ‘Bring forth the best robe and put it on him; and put a ring on his hand, and shoes on his feet: and bring hither the fatted calf, and kill it; and let us eat, and be merry: for this is My son who was dead, and is alive again; and he was lost, and is found. And they began to be merry.’ (Luke 16:22-24) And this is taking place for each and every one of us, and for the sake of every sinner who repents. Namely, joy and happiness is taking place in the heaven of the All-merciful Lord and God, and together with Him, all of the holy angels.

St. Justin Martyr

He who will not accept a reproof, just or unjust, renounces his own salvation. But he who accepts it with an effort, or even without an effort, will soon receive the remission of his sins.

St. John Climacus

A penitent is an undisgraced convict. Repentance is reconciliation with the Lord by the practice of good deeds contrary to the sins.

St. John Climacus

You came into the world to save sinners; therefore You came to save Me also? You came to find and to save him who was lost; therefore You came to seek me too, for I am one of the lost. O Lord, O my God and Creator! I should have come to You as a transgressor of Your law. I should have fallen at Your feet, cast myself down before You, humbly begging forgiveness, pleading with You and craving Your mercy. But You Yourself have come to me, wretched and good-for-nothing servant that I am; my Lord has come to me, His enemy and apostate; my Master has come and has bestowed his love of mankind upon me. Listen my soul: God has come to us.

St. Tikhon of Zadonsk

Repentance is the renewal of baptism. Repentance is a contract with God for a second life. 

St. John Climacus

By resolving to make one's confession, the soul is thereby held from sinning as by a bridle. For what we do not confess, that we do fearlessly as though in the dark.

St. John Climacus

 I ask you to try something. If someone grieves you, or dishonors you, or takes something of yours, then pray like this: “Lord, we are all your creatures. Pity your servants, and turn them to repentance,” and then you will perceptibly bear grace in your soul. Induce your heart to love your enemies, and the Lord, seeing your good will, shall help you in all things, and will Himself show you experience. But whoever thinks evil of his enemies does not have love for God and has not known God.

St. Silouan the Athonite

I judge my own case: if the Lord so loved me, it must mean that He loves all sinners in the same measure as He loves me.

St. Silouan the Athonite

 The compassionate God still calls to Himself all that have turned away, and He awaits them and promises them mercy.

St. Tikhon of Zadonsk

Years are not needed for true repentance, and not days, but only an instant.

St. Ambrose of Optina

Have confidence in the compassion of our Creator. Reflect well on what you are now doing, and keep before you the things you have done. Lift up your eyes to the overflowing compassion of heaven, and while He waits for you, draw near in tears to our merciful Judge. Having before your mind that He is a Just Judge, do not take your sins lightly; and having also in mind that He is compassionate, do not despair. The God-Man gives man confidence before God.

St. Gregory the Great

God is loving to man, and loving in no small measure. For say not, I have committed fornication and adultery: I have done dreadful things, and not once only, but often: will He forgive? Will He grant pardon? Hear what the Psalmist says: "How great is the multitude of Your goodness, O Lord!" 

Your accumulated offenses surpass not the multitude of God’s mercies: your wounds surpass not the great Physician’s skill. Only give yourself up in faith: tell the Physician your ailment: say thou also, like David: "I said, I will confess me my sin unto the Lord": and the same shall be done in your case, which he says immediately: "And you forgave the wickedness of my heart.”

St. Cyril of Jerusalem

Through repentance the filth of our foul actions is washed away. After this, we participate in the Holy Spirit, not automatically, but according to the faith, humility and inner disposition of the repentance in which our soul is engaged. For this reason it is good to repent each day as the act of repentance is unending.

St Symeon the New Theologian 

It is not enough to simply make your confession to the Spiritual Father; you must also truly repent of what you have done.

St. Paisios of Mount Athos 

Why do we judge our neighbors? Because we shun knowing ourselves. Someone busy trying to understand himself has no time to notice the shortcomings of others. Judge yourself ... and you will stop judging others. Judge a poor deed, but do not judge the doer. It is necessary to consider yourself the most sinful of all, and to forgive your neighbor every poor deed.

St. Seraphim of Sarov

If the Lord were not long-suffering, if He were not the Lover of men, would He have borne with our great offences? Would He have been incarnate? Would He have suffered and died for you? Would He have given you His most pure Body and Blood, upon which even the angels look with fear and trembling? Would He have saved you from sin and spiritual death so many innumerable times?

St. John of Kronstadt 

How many times, after I had sinned, You comforted me, as a good Father, and You kissed me warmly as a son or a daughter, and You stretched out Your arms to me and cried out: rise up, fear not, stand up, come! 

St John of Damascus 

 Do we forgive our neighbors their trespasses? God also forgives us in His mercy. Do we refuse to forgive? God, too, will refuse to forgive us. As we treat our neighbors, so also does God treat us. The forgiveness, then, of your sins or unforgiveness, and hence also your salvation or destruction, depend on you yourself, man. For without forgiveness of sins there is no salvation.

St. Tikhon of Zadonsk