Halakhah sa Mga Awit 92:3: Mishneh Torah, Reading the Shema

The first of the blessings recited before the Shema, whether by day or at night, is introduced with the formula, "Blessed [art Thou, O Lord our God, King of the Universe]" and concludes with the formula, "Blessed [art Thou, O Lord]." Of the other blessings, each concludes with the formula, "Blessed [art Thou, O Lord]" but are not introduced with the formula, "Blessed art Thou …" These blessings as well as all the other blessings with which all Israel are familiar were instituted by Ezra and his court and no one is permitted to take aught away from the wording or add to it. The blessings which they (Ezra and his colleagues) ordained to conclude with the formula, "Blessed [art Thou etc.]" may not be recited without this formula. Those which they ordained should conclude without this formula may not be recited with it. Those which they ordained not to begin with a benedictory formula, may not be begun with it. Those which they ordained should begin with it may not be begun without it. In short, whoever alters the form the Sages gave to the blessings commits an error and must recite the blessing again according to its prescribed form. Whoever does not recite the blessing beginning, "True and firm" in the morning, and that beginning, "True and trustworthy" in the evening has not fulfilled his duty.