Theophylact of Ohrid

He commands them to take nothing — neither a bag, nor money in their belt, nor bread — so as to teach them detachment from possessions and so that others, looking at them, might be moved to compunction when they teach non-possessiveness by themselves having nothing. Indeed, who would not be moved to compunction and stirred toward non-possessiveness, seeing that an apostle takes neither a bag nor bread, which is the most necessary thing for us?

Commentary on Mark ↗

Augustine of Hippo

Or else; according to Matthew (Matt. 10:19), the Lord immediately subjoined, The workman is worthy of his meat, which sufficiently proves why He forbade their carrying or possessing such things; not because they were not necessary, but because He sent them in such a way as to show, that they were due to them from the faithful, to whom they preached the Gospel. …

Catena Aurea by Aquinas ↗

Jerome

Are all commanded not to have two coats, nor food in their possession, money in their purse, only a staff in the hand and shoes on the feet? Are all commanded to sell all they possess and give it to the poor, and follow Jesus? Of course not. This command is for those who earnestly desire to respond fully to grace.… The Lord says in the Gospel to him who had boasted of having kept the whole law: "If you will be perfect, go and sell all that you have, and give to the poor, and come, follow me." He said this to those who wish to be …

Against Jovinianus 2.6 ↗

Bede

Again, allegorically; under the figure of a scrip is pointed out the burdens of this world, by bread is meant temporal delights, by money in the purse, the hiding of wisdom; because he who receives the office of a doctor, should neither be weighed down by the burden of worldly affairs, nor be made soft by carnal desires, nor hide the talent of the word committed to him under the ease of an inactive body. …

Catena Aurea by Aquinas ↗