He heard Mary conversing with the apostle John

At night Gregory beheld the foundation of the faith. Various thoughts troubled him, for certain people perverted true teaching and often obscured it through persuasive, clever attempts.

As he laid awake, there appeared to him in a vision an aged person in human form adorned with solemn raiment and whose countenance was striking by great virtue and kindness in addition to the integrity its form. Gregory was struck by fear at this sight and rising up from bed, realized who he was and why he came. After quieting his fear, he said in a soft voice that a divine order bade him to appear, the reasons of which were obscure to Gregory, in order to reveal the truth of correct belief and to encourage him to speak while gazing upon him with both joy and respect. Then the old man suddenly extended his hand and with his finger pointed to something which appeared near him which was a splendid female form instead of a male one.

Once again Gregory was terrified and turned his face away, unable to bear its sight. The vision was especially amazing since the night was gloomy, for it resembled something like a light illuminated by another light. Since he could not look upon this spectacle, he heard from those who appeared to him speaking in detail about what he was seeking. Not only was he revered with regard to true knowledge of faith but recognized the names of each man who appeared when they called each other by their respective names.

It is claimed that this vision of a female form told Gregory that the evangelist John was exhorted to manifest the mystery of truth to a young man, saying that she was chosen to be the mother of the Lord whom she cherished. He also said that this fitting vision had vanished again from his sight. He was immediately ordered to write down this divine revelation and later proclaim it in the church. In this way it became for others a divinely given legacy through which the people might repulse any evil of heresy.

Apparition of Mary and John the Evangelist to Saint Gregory the Wonderworker,

As told by Saint Gregory of Nyssa (d. 394)