John Chrysostom

Now this happened in the case of the manna. For both they that gathered more, and they that gathered less, were found to have the same quantity, God in this way punishing insatiableness. And this he said at once both to alarm them by what then happened, and to persuade them never to desire to have more nor to grieve at having less. And this one may see happening now in things of this life not in the manna only. …

Homily 17 on 2 Corinthians ↗

Theophylact of Ohrid

How will there be equality? If both you and they mutually share your surpluses with one another and fill each other's deficiencies. But what kind of equality is it to give spiritual things in return for material things? Here, of course, the equality is not in relation to the value or pricelessness of what is given and received in return, but in relation to surplus and lack: you give from your surplus, and they give from their surplus; and again: you receive what you were in need of, and they receive what they are in need of. …

Commentary on 2 Corinthians ↗

Thomas Aquinas

Then he confirms this with an authority; hence he says, "As it is written," namely in Ex. (16:18): "He who gathered much," i.e., had collected more manna than an omer, "had nothing over," i.e., did not have more than his sufficiency; "and he who gathered little had no lack," i.e., he did not fall short of it, because all had an equal abundance, as it says in Ex. (16:18). And so neither he who had collected more had more, nor he who had prepared less, discovered less.

Commentary on 2 Corinthians ↗