But do ye all, as many as are made glad, by the gift of regeneration, and make your boast of that saving renewal, show me, after the sacramental grace, the change in your ways that should follow it, and make known by the purity of your conversation the difference effected by your transformation for the better.
[...] But there is certainly need of some manifest proof, by which we may recognize the new-born man, discerning by clear tokens the new from the old.
And these I think are to be found in the intentional motions of the soul, whereby it separates itself from its old customary life, and enters on a newer way of conversation, and will clearly teach those acquainted with it that it has become something different from its former self, bearing in it no token by which the old self was recognized.
[...] The man that was before Baptism was wanton, covetous, grasping at the goods of others, a reviler, a liar, a slanderer, and all that is kindred with these things, and consequent from them…:
Let him now become orderly, sober, content with his own possessions, and imparting from them to those in poverty, truthful, courteous, affable—in a word, following every laudable course of conduct.
For as darkness is dispelled by light…, so the old man also disappears when adorned with the works of righteousness.
You see how Zacchæus also by the change of his life slew the publican, making fourfold restitution to those whom he had unjustly damaged, and the rest he divided with the poor—the treasure which he had before got by ill means from the poor whom he oppressed.
[...] Such ought you to be in your regeneration: so ought you to blot out your habits that tend to sin; so ought the sons of God to have their conversation: for after the grace bestowed we are called His children.
And therefore we ought narrowly to scrutinize our Father’s characteristics, that by fashioning and framing ourselves to the likeness of our Father, we may appear true children of Him Who calls us to the adoption according to grace.
[...] The Lord, laying down for us in the Gospels the rules of our life, uses these words to His disciples, “Do good to them that hate you, pray for them that despitefully use you and persecute you; that ye may be the children of your Father which is in heaven….”
For then He says they are sons when in their own modes of thought they are fashioned in loving kindness towards their kindred, after the likeness of the Father’s goodness.
Gregory of Nyssa (c 335 – after 394): A Sermon for the Day of Lights.