Ye are not straitened in us - That is, you do not possess a narrow or contracted place in our affections. We love you fully, ardently, and are ready to do all that can be done for your welfare. There is no lack of room in our affections toward you. It is not narrow, confined, pent up. It is ample and free.
But ye are straitened in your own bowels - That is, in the affections of your hearts. The word used here (σπλάγχνα splangchna) commonly means in the Bible the tender affections. The Greek word properly denotes the upper viscera; the heart, the lungs, the liver. It is applied by Greek writers to denote those parts of victims which were eaten during or after the sacrifice - Robinson (Lexicon). Hence, it is applied to the heart, as the seat of the emotions and passions; and especially the gentler emotions, the tender affections, compassion, pity, love, etc. Our word “bowels” is applied usually to the lower viscera, and by no means expresses the idea of the word which is used in Greek. The idea here is, that they were straitened, or were confined in their affections for him. It is the language of reproof, meaning that he had not received from them the demonstrations of attachment which he had a right to expect, and which was a fair and proportionate return for the love bestowed on them. Probably he refers to the fact that they had formed parties; had admitted false teachers; and had not received his instructions as implicitly and as kindly as they ought to have done.