3 But what was this “his own,” unto which John took the mother of the Lord? For he was not outside the circle of those who said unto Him, “Lo, we have left all, and followed You.” No, but on that same occasion he had also heard the words, Every one that has forsaken these things for my sake, shall receive an hundred times as much in this world. That disciple, therefore, had an hundredfold more than he had cast away, whereunto to receive the mother of Him who had graciously bestowed it all.
But it was in that society that the blessed John had received an hundredfold, where no one called anything his own, but they had all things in common; even as it is recorded in the Acts of the Apostles. For the apostles were as if having nothing, and yet possessing all things. How was it, then, that the disciple and servant received unto his own the mother of his Lord and Master, where no one called anything his own? Or, seeing we read a little further on in the same book, “For as many as were possessors of lands or houses sold them, and brought the prices of them, and laid them down at the apostles' feet: and distribution was made unto every man according as he had need,” are we not to understand that such distribution was made to this disciple of what was needful, that there was also added to it the portion of the blessed Mary, as if she were his mother; and ought we not the rather so to take the words, “From that hour the disciple took her unto his own,” that everything necessary for her was entrusted to his care?
He received her, therefore, not unto his own lands, for he had none of his own; but to his own dutiful services, the discharge of which, by a special dispensation, was entrusted to himself.
Source: Tractates on the Gospel of John (New Advent)