No more faction. On this occasion, I suppose, it was that they received the right hand, as he says himself, “They gave to me and Barnabas right hands of fellowship.” There he says, “They added nothing to me.” For they confirmed his view: they praised and admired it.— It shows that even from human reasonings it is possible to see this, not to say from the Holy Ghost only, that they sinned a sin not easy to be corrected. For such things need not the Spirit.— It shows that the rest are not necessary, but superfluous, seeing these things are necessary. “From which if you keep yourselves,” it says, “you shall do well.” It shows that nothing is lacking to them, but this is sufficient. For it might have been done also without letters, but that there may be a law in writing (they send this Epistle): again, that they may obey the law (the Apostles), also told those men (the same things), and they did this, “and confirmed them, and having tarried a space were let go in peace.”
Source: Homilies on Acts (New Advent)