Musar su Isaia 55:1

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.'"

Onkelos translates the words "the G–d of the Hebrews has called upon us," as "the G–d of the Hebrews has revealed Himself to us" (Exodus 5,3). What he means by this is that a new perspective of the universe had been revealed for the sake of Israel. From now on Israel would be the fruit and everything in the universe would become of secondary importance. The reason Israel would become of primary importance was that they would travel three days' distance into the desert, to receive the Torah. This is in accordance with the statement in Baba Kama 82, that the verse "they walked three days in the desert and did not find water," refers to their not receiving the Torah during that period (Exodus 15,22). We have a tradition that אין מים אלא תורה that the true meaning of "water" is Torah (Baba Kama 17). Their fatigue was due to the absence of Torah, which would have inspired them. Isaiah 55,1, refers to this מים-תורה according to the Talmudic source quoted. It was then that the prophets arranged for public Torah readings on every Sabbath, Monday and Thursday, to insure that Israel would never be without the benefit of Torah for three days.