Theophylact of Ohrid

Denying them any basis for saying that John later became soft by giving himself over to luxury, He says, This cannot be; that his clothing is made of hair shows that he is an enemy of luxury. For if he were wearing soft clothing and living in kings' houses, if he so desired luxury he would not be in prison. So then, learn that it does not befit a true Christian to wear luxurious clothing.

Commentary on Matthew ↗

Augustine of Hippo

In all such things we blame not the use of the things, but the lust of those that use them. For whoever uses the good things in his reach more sparingly than are the habits of those with whom he lives, is either temperate or superstitious. Whoever again uses them in a measure exceeding the practice of the good among whom he lives, either has some meaning therein, or else is dissolute.

Catena Aurea by Aquinas ↗

Jerome

But as they were departing, Jesus began to speak to the crowds about John: What did you go out into the wilderness to see? A reed shaken by the wind? But what did you go out to see? A man dressed in soft clothing? Look, those who wear soft clothing are in the palaces of kings. If a harsh judgment had been pronounced against John, as many believe, then why is he now being praised so highly? …

Commentary on Matthew ↗

Gregory the Dialogist

Let no one suppose that there is nothing sinful in luxury and rich dress; if pursuit of such things had been blameless, the Lord would not have thus commended John for the coarseness of his raiment, nor would Peter have checked the desire of fine clothes in women as he does, Not in costly raiment. (1 Pet. 3:3) (ubi. …

Catena Aurea by Aquinas ↗