John Chrysostom

Since he had said that I have no longer "more place in these parts," and, "I have a great desire, these many years, to come unto you," but he still intended to delay; lest it should be thought that he was making a jest of them, he mentions the cause also why he still puts it off, and he says, that "I am going unto Jerusalem," and is apparently giving the excuse for the delay. But by means of this he also makes good another object, which is the exhorting of them to alms, and making them more in earnest about it. …

Homily on Romans 30 ↗

Theophylact of Ohrid

Above he gave a promise to come to them. In the meantime he still needed to delay. Therefore, lest they think he was mocking them, he states the reason for his delay and says: "I go to Jerusalem to minister to the saints." He did not say: carrying alms with me, but: "to minister," so that we might learn how lofty, by whom it is performed, and how important this is.

Commentary on Romans ↗

Thomas Aquinas

Then when he says, but now I shall go, he tells why he must postpone his visit. In regard to this he does three things: first, he gives the reason, saying: but now I shall go, i.e., I am not coming to you at once, because now I shall go to Jerusalem to minister to the saints. In this regard what is written in Acts 4:34 et seq. …

Commentary on Romans ↗