Here’s how Melito, a bishop of Sardis in the 2nd century, explained it:
“For there is no need, to persons of intelligence, to attempt to prove, from the deeds of Christ subsequent to His baptism, that His soul and His body, His human nature like ours, were real, and no phantom of the imagination. For the deeds done by Christ after His baptism, and especially His miracles, gave indication and assurance to the world of the Deity hidden in His flesh. For, being at once both God and perfect man likewise, He gave us sure indications of His two natures: of His Deity, by His miracles during the three years that elapsed after His baptism; of His humanity, during the thirty similar periods which preceded His baptism, in which, by reason of His low estate as regards the flesh, He concealed the signs of His Deity, although He was the true God existing before all ages.”
and
“On these accounts He came to us; on these accounts, though He was incorporeal, He formed for Himself a body after our fashion, -appearing as a sheep, yet still remaining the Shepherd; being esteemed a servant, yet not renouncing the Sonship; being carried in the womb of Mary, yet arrayed in the nature of His Father; treading upon the earth, yet filling heaven; appearing as an infant, yet not discarding the eternity of His nature; being invested with a body, yet not circumscribing the unmixed simplicity of His Godhead; being esteemed poor, yet not divested of His riches; needing sustenance inasmuch as He was man, yet not ceasing to feed the entire world inasmuch as He is God; putting on the likeness of a servant, yet not impairing the likeness of His Father. He sustained every character belonging to Him in an immutable nature: He was standing before Pilate, and at the same time was sitting with His Father; He was nailed upon the tree, and yet was the Lord of all things.”
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