John 1:38

38.Rabbi. This name was commonly given to persons of high rank, or who possessed any kind of honor. But the Evangelist here points out another use of it which was made in his own age, which was, that they addressed by this name the teachers and expounders of the word of God. Although, therefore, those two disciples do not yet recognize Christ as the only Teacher of the Church, yet, moved by the commendation bestowed on him by John the Baptist, they hold him to be a Prophet and teacher, which is the first step towards receiving instruction.

Where dwellest thou? By this example we are taught that from the first, rudiments of the Church we ought to draw such a relish for Christ as will excite our desire to profit; and next, that we ought not to be satisfied with a mere passing look, but that we ought to seek his dwelling, that he may receive us as guests. For there are very many who smell the gospel at a distance only, and thus allow Christ suddenly to disappear, and all that they have learned concerning him to pass away. And though those two persons did not at that time become his ordinary disciples, yet there can be no doubt that, during that night, he instructed them more fully, so that they soon afterwards became entirely devoted to him.