Theophylact of Ohrid — as excerpted in the Catena Aurea on Mark 6:6-13

“Again He sends the Apostles two and two that they, might become more active; for, as says the Preacher, Two are better than one. (Eccl. 4:9) But if He had sent more than two, there would not have been a sufficient number to allow of their being sent to many villages.”