TT #23 · Parashas Va’eschanan · Passuk 6:7
And you shall teach them diligently to your children, and you shall speak of them when you sit in your house, and when you walk on the way, and when you lie down, and when you rise up.
Torah Temimah points to the classic derashos of “veshinantam” (sharp, repeated teaching) and the times of day that define the obligation of Keri’as Shema (Berachos 2a ff. / Kiddushin 30a).
English: “And you shall teach them diligently (veshinantam) to your children” — so that the words of Torah will be sharp in your mouth: if a person asks you something, you should not stammer and tell him, but rather tell him immediately.
Diyuk of the verb “veshinantam” (sharpen / repeat).
Torah must be taught so thoroughly that it is sharp and ready on the tongue; the teacher must be able to answer at once.