John 13:3 does NOT say Jesus 'took the form of a servant', CORRECT. That's
Philippians 2:7.
John 13:4: ἐγείρεται ἐκ τοῦ δείπνου καὶ τίθησιν τὰ ἱμάτια καὶ λαβὼν
λέντιον διέζωσεν ἑαυτόν·
λέντιον = Linen, apron.
John 13:5: Then he poured water into a basin and began to wash the disciples’ feet and to wipe them with the towel that was tied around him.
Jesus does a servant's work. He had become a servant (implied). Totally nude?
Augustine, Tractate
55.7 (John 13:1-5) c.415 AD:
And why should we wonder, if He girded Himself with a towel, who took upon Him the form of a servant, and was found in the likeness of a man?
This? Where "formam servi accipiens" is the δούλου of
Philippians 2:7.
Hic est enim qui cum in forma Dei esset, non rapinam arbitratus est esse aequalis Deo, sed semetipsum exinanivit, formam servi accipiens, in similitudinem hominum factus, et habitu inventus ut homo; humiliavit semetipsum, factus obediens usque ad mortem, mortem autem crucis.
The Argument over the Towel in John Chrysostom,
Homily 7 on Philippians is c.395:
What then say the heretics? See, say they, He did not become man. The Marcionites, I mean. But why? He was "made in the likeness of man." But how can one be "made in the likeness of men"? By putting on a shadow? But this is a phantom, and no longer the likeness of a man, for the likeness of a man is another man. And what will you answer to John, when he says, "The Word became flesh"? John 1:14 But this same blessed one himself also says in another place, "in the likeness of sinful flesh." Romans 8:3
...
"And being found in fashion as a man." See, they say, both "in fashion," and "as a man." To be as a man, and to be a man in fashion, is not to be a man indeed. To be a man in fashion is not to be a man by nature. See with what ingenuousness I lay down what our enemies say, for that is a brilliant victory, and amply gained, when we do not conceal what seem to be their strong points. For this is deceit rather than victory. What then do they say? Let me repeat their argument. To be a man in fashion is not to be a man by nature; and to be as a man, and in the fashion of a man, this is not to be a man. So then to take the form of a servant, is not to take the form of a servant. Here then is an inconsistency; and wherefore do you not first of all solve this difficulty? For as you think that this contradicts us, so do we say that the other contradicts you. He says not, "as the form of a servant," nor "in the likeness of the form of a servant," nor "in the fashion of the form of a servant," but "He took the form of a servant." What then is this? For there is a contradiction. There is no contradiction. God forbid! It is a cold and ridiculous argument of theirs. He took, say they, the form of a servant, when He girded Himself with a towel, and washed the feet of His disciples. Is this the form of a servant? Nay, this is not the form, but the work of a servant. It is one thing that there should be the work of a servant, and another to take the form of a servant. Why did he not say, He did the work of a servant, which were clearer? But nowhere in Scripture is "form" put for "work," for the difference is great: the one is the result of nature, the other of action. In common speaking, too, we never use "form" for "work." Besides, according to them, He did not even take the work of a servant, nor even gird Himself. For if all was a mere shadow, there was no reality. If He had not real hands, how did He wash their feet? If He had not real loins, how did He gird Himself with a towel? And what kind of garments did he take? For Scripture says, "He took His garments." John 13:12 So then not even the work is found to have really taken place, but it was all a deception, nor did He even wash the disciples. For if that incorporeal nature did not appear, it was not in a body. Who then washed the disciples' feet?
"That Augustine had read Chrysostom is evident in his work
Contra Julianum. Apparently, Julian had cited Chrysostom as supporting the belief that infants, even before baptism, are free of original sin..." Augustine citing the work of someone he knew 419 AD is acceptable; that both knew and discussed the prolific and famous writings of the recent Church leader (Chrysostom, Archbishop of Constantinople c.395 AD), i.e. a 25 years old work, is entirely plausible.
Therapeutae were 'servants of God' but that is not mentioned here, too problematic, for the distinction between 'serving God' and 'serving man,' and what had seemed so obvious to Eusebius
c.325 AD. I find it curious that Augustine would be ignorant of that older work -- a century, almost three generations -- but many reasons may be given for omission. I suppose the Jesus-as-a-Therapeut argument had been largely abandoned c.350 AD, a forbidden history as Church dogma took root.