After a brief chronology of the sojourn in the desert, Moshe begins to review the mitvzahs of the Torah. The first sentence of this compendium is the sentence that, to this day, awakens Jewish consciousness in the heart of every Jew. It is the first sentence a Jewish child learns, and it is the last sentence on his lips when he leaves this world. It is the sentence inscribed on the banner which the Jews have carried throughout history, and with this sentence they declare that G-d will ultimately “reconquer” mankind. It is the last sentence that a Jew who has been alienated from his people would discard. Whenever a Jew lies down or rises, wherever he builds his home and places his doors, this verse reminds him of his life’s mission, and of the principles that guide his thought and conduct.
Why do we say, “Hear, O, Israel,” and not, “See, O, Israel?” Moshe has just recounted how the people’s knowledge of G-d is based on seeing, and not on hearing! (“You have been made known by sight that G-d alone is G-d; there is none beside Him,”
Devarim 4:35). Indeed, their knowledge of G-d was based on seeing. However, only one time in history did G-d enter the earthly present and reveal Himself — when laying the foundation for the creation of His people. From then on, one generation will tell another about that Revelation. And by means of this tradition, the revelation will remain the indisputable basis for all the thoughts and actions of every man of Israel. Thus, “Hear, O, Israel.”
Had we been instructed to “see,” man would have been led to search his experiences in nature and history for the existence of G-d, reaching conclusions only by speculative inference and deduction — mere belief. But our knowledge of G-d is bound with the certainty of revelation, rooted in a sensory perception which the entire nation experienced. Our fathers saw
G-d in nature and history when He redeemed them from Egypt. They heard
G-d when He gave them the Torah. This testimony, attested to by the entire nation, is the basis of our knowledge.
Once knowledge exists, we can then open our eyes to see His workings in nature and open our ears to hear His voice in history. Instead of speculating by deduction, we affirm that everything great and small in nature is His work and everything treat and small in history is an act of His providence.
The first fundamental truth of our knowledge is “echad” — G-d is one and alone. Although the world is full of contrary phenomena, it is the one G-d who willed and upholds all of these contrasts. What appears to be dual is in fact part of the same rule and purpose — Hashem (the Name of mercy), Elokeinu (the Name of justice), Hashem is one. Even when He appears as Elokim in justice, He is Hashem, in love and compassion.
Sources: Commentary, Devarim 6:4