For that he might not seem to be holding them very cheap, by saying, Since I have not anything to do, therefore I am coming to you, he again touches on the point of love by saying, “I have a great desire, these many years, to come unto you.” For the reason why I desire to come, is not because I am disengaged, but that I may give birth to that desire wherewith I am travailing so long. Then that this again should not puff them up, consider how he lowers them by saying, “Whenever I take my journey into Spain, I trust to see you in my journey.”
For this was why he stated this, that they should not be high-minded. For what he wants is to show his love, and at the same time to prevent them from being dainty. And so he places this close on the other, and uses things confirmative of either alternately. For this reason again that they might not say, Do you make us a by-object of your journey? He adds, and to be brought on my way thitherward by you: that is, that you may be my witnesses that it is not through any slight of you, but by force of necessity, that I run by you.
But as this is still distressing, he heals it over more carefully, by saying, “If I be first somewhat filled with your company.” For by his saying, “in my journey,” he shows that he did not covet their good opinion. But by saying “be filled,” that he was eager for their love, and not only was eager for it, but exceedingly so; and this is why he does not say “be filled,” but be “somewhat” so. That is, no length of time can fill me or create in me a satiety of your company. See how he shows his love, when even though in haste he does not rise up until he be filled.
And this is a sign of his great affectionateness, that he uses his words in so warm a way. For he does not say even I will see, but “shall be filled,” imitating thus the language of parents. And at the beginning he said, “that I might have some fruit.” But here that I may be “filled.” And both these are like a person who is drawing others to him. For the one was a very great commendation of them, if they were likely to yield him fruit from their obedience; and the other, a genuine proof of his own friendship.
And in writing to the Corinthians he thus says, “That ye may bring me on my journey wherever I go”, so in all ways exhibiting an unrivalled love to his disciples. And so at the beginning of all his Epistles it is with this he starts, and at the end in this he concludes again. For as an indulgent father does an only and true born son, so did he love all the faithful. Whence it was that he said, “Who is weak, and I am not weak? Who is offended, and I burn not?”
Source: Homilies on Romans (New Advent)