Wherefore he nowhere says, 'the richness of the gifts,' but "the riches of their liberality." Now what he says is to this effect; 'their poverty not only was no impediment to their being bountiful, but was even an occasion to them of abounding, just as affliction was of feeling joy. For the poorer they were, the more munificent they were and contributed the more readily.' Wherefore also he admires them exceedingly, for that in the midst of so great poverty they had displayed so great munificence. For "their deep," that is, 'their great and unspeakable,' "poverty," showed their "liberality." But he said not 'showed,' but "abounded;" and he said not "liberality," but "riches of liberality;" that is, an equipoise to the greatness of their poverty, or rather much outweighing it, was the bountifulness they displayed. Then he even explains this more clearly, saying, "For according to their power, I bear witness." Trustworthy is the witness. "And beyond their power." That is, it "abounded unto the riches of their liberality." Or rather, he makes this plain, not by this expression alone, but also by all that follows; for he says, "of their own accord." Lo! yet another excessiveness.
[AD 384] Ambrosiaster on 2 Corinthians 8:3