“And you shall speak about them….. when you lie down and when you get up” (Devarim 6,7)
It is a positive commandment to read the verse “Listen, Yisrael, Hashem is your G-d, Hashem is One” every day, in the evening and in the morning, for regarding this verse it says, “and you shall speak about them when you sit in your house, when you lie down and when you get up.” Chazal explain this; a person must read this verse at the time when people lie down and at the time when people get up. (It must be pointed out that many of the Rishonim disagree with this and say that the Biblical obligation is to read also the paragraphs that follow the Shema).
Amongst the roots of this commandment are that Hashem wanted to merit His people by commanding them to accept upon themselves His dominion and His Oneness every day, both by day and by night, every day of their lives. This is because since a person is a physical entity and is enticed by the emptiness of this world and drawn after his desires, he therefore needs a constant reminder of the kingdom of heaven to keep him from sin. Therefore, out of His kindness He merited us and commanded us to remember twice regularly and with full concentration, once a day to affect all of our actions during the day, for when every morning, a person remembers the Oneness of Hashem and His dominion, and that His control and His supervision are over everything, and he internalizes the fact that His eyes are watching all his ways, and all his steps are counted, not one of his deeds is hidden from Him, and he cannot hide from Him even one of his thoughts, surely this thought and this utterance will be a guard over him all that day?! And one time at night – that the utterance of the night should protect him all night.
And because this is the foundation of the commandment, a person must concentrate his heart fully and if he did not concentrate, he has not fulfilled (the commandment), for a person cannot remember something unless he concentrates on it. Chazal say that a person must lengthen his pronunciation of the word “Echad”, and one who lengthens his pronunciation of Echad, his days and years will be lengthened, and the lengthening is the amount of time that he focuses on Hashem’s dominion over the heavens and earth and on all four directions of the world, that is to say, that a person should focus on the fact that His dominion is over everything and nothing is hidden from Him and it is through His will that everything exists.
AMongst the laws of the commandment are, that (the saying of) the first verse is a Biblical obligation but Chazal have obligated us to read all three chapters which are “Shema” “Vehaya ” and “vayomer” and when a person remembers these once a day and once a night, he will be saved from sin, if he has any understanding.
Within the realms of this commandment is that Chazal have obligated us to recite blessings before and after reading Shema, in Shacharis there are two blessings preceding it “Yotzer Or” and “Ahavas Olam” and one following it “Emes veyatziv“ and in the evening two preceding it “Emes ve’emuna” and “Hashkivenu” and Ezra the scribe and his Beth Din established them with all the other blessings that all Jews are familiar with.
Also in the realms of this commandment, is that one who reads the Shema must read it loud enough to hear it, and if he doesn’t hear it, but nonetheless read the words with his lips, he has still fulfilled his obligation.
This commandment applies in every place, at every time, to men but not to women since it is a positive commandment with a fixed time. One who does not read the Shema every day and every night at the time which Chazal have fixed for it has transgressed this positive commandment.