John Chrysostom

"Ye are not straitened in us, but ye are straitened in your own affections." And this reproof, see it administered with forbearance, as is the wont of such as love exceedingly. He did not say, 'ye do not love us,' but, 'not in the same measure,' for he does not wish to touch them too sensibly. 'You receive one,' he says, 'but I a whole city, and so great a population.' And he said not, 'ye do not receive us,' but, 'ye are straitened;' implying indeed the same thing but with forbearance and without touching them too deeply.

Homily 13 on 2 Corinthians ↗

Theophylact of Ohrid

You, he says, are not cramped in my heart, a heart spacious enough no matter how many of you there are. But in your hearts there is great narrowness, and you cannot spaciously accommodate me, though I am but one. That is, I love you to the highest degree, but you, although you love me and have me in your hearts, do so in a cramped way, not spaciously.

Commentary on 2 Corinthians ↗

Thomas Aquinas

Then he shows that they have no contrary example from the Apostle, saying, You are not restricted by us [straightened]. As if to say: from the fact that we show you the largeness of our heart, you do not have an example or a reason why you should be straightened. But if you do this, then indeed you are straightened, but not by us, but in your own affections, i.e., by yourselves. Here it should be noted that to be straightened is the same as to be enclosed in something, from which no exit appears. …

Commentary on 2 Corinthians ↗