From Homily 5 on Titus (ca. 394)

Do not think that grace stops at the pardon of former sins— it secures us against them in the future… Our great God and Savior, he who saved us when we were enemies, what will he not do then when he has us approved?… Therefore, Paul says, “Revile no one, for such were you.” We were sometimes foolish, disobedient, deceived, serving various lusts and pleasures, living in malice and envy, hateful, and hating one another. Therefore, we ought to be gently disposed to all. For he who was formerly in such a state and has been delivered from it, ought not to reproach others, but to pray, to be thankful to God who has granted both to him and to other sinners deliverance from such evils. Let no one boast; for all have sinned.

If then, doing well yourself, you are inclined to revile others, consider your own former life, and the uncertainty of the future, and restrain your anger. For if you have lived virtuously from your earliest youth, yet nevertheless you may have many sins; and if you have not, as you think, consider that this is not the effect of your virtue, but of the grace of God… the kindness and love of God our Savior toward man… How did this come? Not by works of righteousness which we have done, but according to his mercy he saved us by the washing of regeneration and the renewing of the Holy Spirit.

Strange! How were we drowned in wickedness, so that we could not be purified, but needed a new birth? For this is implied by regeneration. For as when a house is in a ruinous state no one places props under it, nor makes any addition to the old building, but pulls it down to its foundations, and rebuilds it anew; so in our case, God has not repaired us, but has made us anew. For this is the renewing of the Holy Ghost. He has made us new men. How? By his Spirit; and to show this further, Paul adds, “which He shed on us abundantly through Jesus Christ our Savior.” Thus we need the Spirit abundantly. That being justified by His grace… we may be made heirs according to the hope of eternal life. At the same time there is an incitement to humility, and a hope for the future. For if when we were so abandoned, as to require to be born again, to be saved by grace, to have no good in us, if then He saved us, much more will He save us in the world to come.

St. John Chrysostom (ca. 347-407) was Archbishop of Constantinople, and one of the greatest preachers of his era. He is traditionally counted among the Four Great Doctors of the Eastern Church.  The Homilies on Titus were preached during his early ministry in Antioch. His feast day is September 13. The text has been adapted for contemporary readers.