Dear Mor Ephrem,
Actually, a number of saints have talked about Theosis in this way, St Peter in his epistles "partaking of the Divine Nature," St Augustine, St John Chrysostom, St Gregory Palamas, but I would have to look up the specific references at home.
My place of employment has a library, but it's short on theological texts . . .
(St Augustine once exclaimed about a Christian who has just received Holy Communion, "You are God!").
Theosis or Divinization is about our actual participation in and transformation by the Uncreated Energies of God.
Through our life in Christ by means of the Holy Spirit and the Will of the Father, we are transfigured, as Christ was on Mt. Tabor, and as the Saints are.
Our very bodies become Christ-like and will be forever, just as Christ's Resurrected Body was and is and always will be.
We become by Grace what God is by nature.
We do not somehow become "God " or else indistinguishable from Him, for that would be intolerable heresy (something promoted by Garner Ted Armstrong and his binitarian group).
We will become "god-like" and our bodies will have the powers that Christ demonstrated following His Resurrection.
It is the presence of the Holy Trinity within us, as God's Temple, that effects this transfiguration in us.
Just as God completely assumed our nature in the Incarnation of Christ, so He not only saved it, but elevated it to heaven through Theosis.
My take on it, anyway!
Alex