Musar su Salmi 19:10

And in Sifrei, Parshath Ekev we find (Mishlei 5:16): "'Then your springs [of Torah] will spread outwards': Words of Torah are compared to water. Just as water lives forever, so, words of Torah live forever, as it is written (Ibid. 4:2): 'For they are life to him who finds them, and to all of his flesh, healing.' And just as water raises the unclean one from his uncleanliness, so, words of Torah raise one from uncleanliness to purity, as it is written (Psalms 19:10): 'The fear of the L-rd is pure.' [And, just as water purifies a man, though the uncleanliness has spread through all of his limbs, so, Torah purifies a man from the uncleanliness of his sins, even if it has spread throughout him, from the soul of his foot until his head. And just as a man is not purified until the water rises over all of his limbs, and there be nothing intervening between his limbs and the water, so, he must subject all of his body and his limbs, in truth, to Torah, with nothing intervening, as it is written (Devarim 6:6): 'And these words shall be … upon your heart']. And just as water restores a man's soul, so do words of Torah restore a man's soul from the way of evil to the way of good, as it is written (Psalms 19:8): 'The Torah of the L-rd is complete, restoring the soul,.' And just as water is free for the world, so is Torah free for the world, as it is written (Isaiah 55:1): "Ho! all who are thirsty, go to the water [of Torah]." Lest you say: 'Just as water has no valuation, so, Torah has no valuation; it is, therefore, written [to negate this] (Mishlei 3:15): 'It is more precious than pearls and all of your desires cannot be compared to it.'"

We are also to "unite" i.e. cleave to Torah scholars upon whom there rests a spirit of purity in contradistinction to association with pagans who are surrounded by a spirit of impurity. Since words of Torah are halachically incapable of becoming impure, association with Torah scholars from whom these words issue is part of displaying reverence for G–d. When the Psalmist 19,10 speaks about יראת ה' טהורה עומדת לעד, that reverence for G–d is pure and endures forever, he alludes to the fact that the words of the Torah retain their purity forever.

Now we see that everything depends upon Fear of Heaven, and that the whole Torah is of no use to a man unless it is accompanied by Fear of Heaven, which is the very peg upon which everything hangs. And it is Fear of Heaven alone that stands by a man forever and ever. And thus did David testify, "The fear of the Lord is clean, enduring for ever" (Ps. 19:10). And thus also King Solomon testified and said, "And God hath so made it, that men should fear before Him (Eccl, 3:14). And it is written, "Better a little with the fear of the Lord, than great treasure and turmoil therewith" (Prov. 15:16).