The Chachamim instituted the recital of three berachot with Keriat Shema of Shacharit, two before the Shema and one after it (Mishnah, Berachot 11a). These berachot add to the content of Keriat Shema, including praise and thanksgiving to Hashem for creating and ruling over the world.
In Keriat Shema we say “Hashem Echad” (“Hashem is One”), denoting that He is the single entity that constitutes and fills the whole world with His oneness. In the first berachah of Keriat Shema, we expand on this foundation. By praising Him for the light that is renewed daily, we extol Hashem, “Who constantly renews the events of creation every day.” In order to emphasize His all-encompassing domain, we mention that He also created the darkness. At night, in the parallel berachah, together with the praise that He is “Ma’ariv aravim” (“the One Who brings on evening”), we add that he is “Borei yom valaylah” (“the Creator of day and night”). Hence, in the first berachah, our belief in God’s unity is given more expanded expression.
Opening with the words “Shema Yisrael” (“Hear O Israel”) expresses our belief that God’s unity is revealed to the world via the nation of Israel, which was expressly created for that purpose. This idea is expanded upon in the second berachah, in which we thank Hashem for the love that He feels for us and for giving us the Torah. We pray that we merit understanding the Torah and fulfill it with love, thereby revealing Hashem’s Name in the world.
“Hashem Elokeinu” (“Hashem our God”) means that Hashem is omnipotent and rules over the world according to His will. His control of the world, with all its forces and components, was revealed most clearly in the exodus from Egypt, which is mentioned at the end of Keriat Shema. This, too, is revealed through the nation of Israel. In the third berachah we expand on this foundation and praise Hashem, “You are the first and You are the last, and aside from You we have no king, redeemer, or savior. From Egypt You redeemed us…” Additionally, we mention the slaying of the firstborn in Egypt and the splitting of the Sea. We then conclude, “Blessed are You, Hashem, Who redeems Israel.”
We see, therefore, that all three berachot are a continuation of, and an expansion on, the foundations of faith that are found in Keriat Shema.
Although the proper order that the Chachamim established is to say Keriat Shema with its berachot, nevertheless, one’s neglect to recite one of them does not prevent him from fulfilling the mitzvah of the other. If a person recites Shema without its berachot he still fulfills the mitzvah of Keriat Shema, and if he recites the berachot without saying Keriat Shema he still fulfills the mitzvah of reciting the berachot. Similarly, one’s neglect to recite one berachah does not hamper the recital of the others. Therefore, if a person recites one of the berachot, he fulfills his obligation over the blessing which he recites. All the more so, reciting the berachot in the wrong order does not prevent one from fulfilling his obligation to say them, so if someone mistakenly recites the second berachah before the first, he still fulfills his obligation. However, l’chatchilah, one must recite all the berachot together in the order that the Chachamim established.