Gregory of Nazianzus, on Ps 83:7

“In the vale of tears, in the place which be hath set.”

“The Old Testament proclaimed the Father openly and the Son more obscurely. The New [Testament] manifested the Son and suggested the deity of the Spirit. Now the Spirit dwells among us and supplies us with a clearer demonstration of himself. For it was not safe, when the Godhead of the Father was not yet acknowledged, plainly to proclaim the Son; nor when that of the Son was not yet received to burden us further (if I may use so bold an expression) with the Holy Spirit; lest perhaps people might, like persons loaded with food beyond their strength and presenting eyes as yet too weak to look at the sun's light, risk the loss even of that which was within the reach of their powers; but that by gradual additions, and, as David says, "Goings up, and advances and progress from glory to glory," the light of the Trinity might shine on the more illuminated. It was for this reason, I think, that [the Holy Spirit] gradually came to dwell in the disciples, measuring himself out to them according to their capacity to receive him, at the beginning of the Gospel, after the passion, after the ascension, making perfect their powers, being breathed on them and appearing in fiery tongues.”

Imported from an open dataset — not yet checked against the printed edition.