Midrash su Salmi 45:6

(Devarim 6:7) "And you shall teach them to your sons": They shall be (well ) ordered in your mouth, so that if one questions you concerning them, you will not stammer in them, but answer him forthwith, as it is written (Proverbs 7:4) "Tell wisdom 'You are my sister,' and call understanding your acquaintance," and (Ibid. 3) "Bind them on your fingers; write them on the tablet of your heart," and (Psalms 45:6) "Your 'arrows' (of learning) are sharp." What is your reward for this? (Ibid.) "Peoples will fall under you, (your arrows piercing) the heart of the foes of the King," and (Ibid. 127:4) "As arrows in the hand of a mighty man, so are the children (i.e., the learning) of youth," and (Ibid. 5) "Happy the man who has filled his quiver with them. They will not be shamed when they speak with the foes (of the L-rd) in the gate (of learning)."