Rav Yosef says that regarding the rest of the Torah (other than shema) everyone agrees that one is required to have his words audible to his ears. Rashi explains this to mean all the other brachos. How can Rav Yosef derive from a passuk a halacah of brachos when we know that brachos are merely of rabbinic origin (other than birchas hamazon)?
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The Rosh says just as birkath hatorah is doraitha and without the bracha one is not mekayem mitzvas talmus tora [al shlo berchu batora] so is any mitzva min hatora like tefilin the brocho is meakev the mitzva
see http://www.hebrewbooks.org/pdfpager.aspx?sits=1&req=9708&st=%u05D1%u05E8%u05DB%u05EA%20%u05D4%u05DE%u05E6%u05D5%u05EA