If now for the first time they believed on Him, they were not His disciples when they came to the marriage. This however is a form of speech, such as saying that the Apostle Paul was born in Tarsus of Cilicia; not meaning by this that he was an Apostle then. In the same way when we hear of Christ’s disciples being invited to the marriage, we should understand not disciples already, but who were to be disciples.
Reproduced in full. Translation: Oxford 1841 (Newman), public domain (Public domain).
Also cites: de Cons. Evang. l. ii c. xvii. [38.]