(Devarim, Ibid.) "And you shall speak in them": Make them (words of Torah) primary and not secondary, that your dealings be only in them, that you not intermix other words with them, that you not say: I have learned the wisdom of Israel; I shall now go and learn the wisdom of the Canaanites. It is, therefore, written (Vayikra 18:4) "to walk therein," and not to depart therefrom. And thus is it written (Proverbs 5:17) "Let them be to you alone and not to strangers with you."
(Devarim, Ibid.) "in your sitting in your house and in your walking upon the way": And thus is it written (Proverbs 6:22) "In your walking it shall lead you; in your lying down it shall guard you; and in your waking it shall speak for you." In your walking it shall lead you" — in this world; "in your lying down" it shall guard you" — at the time of death; "and in your waking": for the days of the Messiah; "it shall speak for you" — for entrance to the world to come.