Mark 9:2

Irenaeus Against Heresies Book I

He asserts that the fruit of this arrangement and analogy has been manifested in the likeness of an image, namely, Him who, after six days, ascended[188]

Tertullian On Monogamy

while, in the revelation of His own glory, He prefers, from among so many saints and prophets, to have with him Moses and Elias[72]

Hippolytus Refutation of All Heresies Book VI

that in the similitude of an image He appeared who after the six days Himself ascended the mountain a fourth person, and became the sixth.[136]

Origen Commentary on Matthew Book XII " according to Matthew and Mark,[227]

Origen Commentary on Matthew Book XII

But hear these things, if you can, at the same time giving heed spiritually, that it is not said simply, "He was trans-figured," but with a certain necessary addition, which Matthew and Mark have recorded; for, according to both, "He was transfigured before them."[229]