1 Subjects strange neither to your ears nor hearts are now repeated: yet do they revive the affections of the hearer, and by repetition in some sort renew us: nor is it wearisome to hear what is well known already, for the words of the Lord are always sweet. The exposition of the sacred Scriptures is as the sacred Scriptures themselves: though they be well known, yet are they read to impress the remembrance of them. And so the exposition of them, though it be well known, is nevertheless to be repeated, that they who have forgotten it may be reminded, or they who chanced not to hear it may hear; and that with those who do retain what they are used to hear, it may by the repetition be brought to pass that they shall not be able to forget it.
For I remember that I have already spoken to you, Beloved, on this lesson of the Gospel. Yet to repeat the same explanation to you is not wearisome, even as it was not wearisome to repeat the same Lesson to you. The Apostle Paul says in a certain Epistle, “To write the same things to you, to me indeed is not wearisome, but for you it is necessary.” So too with myself to say the same things to you, to me is not wearisome, but for you it is safe.
Source: Sermons on Selected Lessons of the New Testament (New Advent)