Irenaeus

He did this when He appeared as a man, that we, being nourished, as it were, from the breast of His flesh, and having, by such a course of milk nourishment, become accustomed to eat and drink the Word of God, may be able also to contain in ourselves the Bread of immortality, which is the Spirit of the Father.

And on this account does Paul declare to the Corinthians, "I have fed you with milk, not with meat, for hitherto ye were not able to bear it." That is, ye have indeed learned the advent of our Lord as a man; nevertheless, because of your infirmity, the Spirit of the Father has not as yet rested upon you. "For when envying and strife," he says, "and dissensions are among you, are ye not carnal, and walk as men?" That is, that the Spirit of the Father was not yet with them, on account of their imperfection and shortcomings of their walk in life. As, therefore, the apostle had the power to give them strong meat-for those upon whom the apostles laid hands received the Holy Spirit, who is the food of life [eternal]-but they were not capable of receiving it, because they had the sentient faculties of the soul still feeble and undisciplined in the practice of things pertaining to God; so, in like manner, God had power at the beginning to grant perfection to man; but as the latter was only recently created, he could not possibly have received it, or even if he had received it, could he have contained it, or containing it, could he have retained it. It was for this reason that the Son of God, although He was perfect, passed through the state of infancy in common with the rest of mankind, partaking of it thus not for His own benefit, but for that of the infantile stage of man's existence, in order that man might be able to receive Him. There was nothing, therefore, impossible to and deficient in God, [implied in the fact] that man was not an uncreated being; but this merely applied to him who was lately created, [namely] man.