When John the Apostle had lived in Ephesus into his extreme old age, and could hardly be carried to the meetings of the church by the disciples, and when in speaking, he could no longer put together many words, he would not say anything else in the meetings but this: “Little children, love one another!” When at last the disciples and brothers present got tired of hearing the same thing again and again, they said, “Master, why do you keep saying the same thing?” John replied with a saying worthy of him: “Because it is the Lord’s command, and it is enough if it is really done.”

Source: The Early Christians