מצות עשה להתפלל בכל יום, שנאמר "ועבדתם, את ה' אלוהיכם
With how he opens Hil Kri’as Shema:
פעמיים בכל יום, קוראים קרית שמע--בערב ובבוקר: שנאמר "ובשוכבך ובקומך
In the former case the Rambam gives us an active voice statement that there is a command to daven every day, but in the latter case the Rambam gives us a passive voice description of what people do every day – read shema – without mentioning any command. Why the difference?
Lechem Mishna explains that the mitzvah of shema is about more than simply reciting a parsha. The mitzvah is really yichud Hashem, acknowledging and accepting that G-d is one. Since that mitzvah of yichud Hashem applies 24x7, therefore the Rambam did not want to write that the mitzvah of shema applies only twice daily.
The GR”A is medayek from the first mishna in Brachos that there is no din of shome’a k’oneh by kri’as shema. Perhaps the reason why is because shomea k’oneh applies only to mitzvos that involve recitation of a text. The mitzvah of kri’as shema is not about reciting a text, but is about the kabbalas ol of yichud Hashem the words are supposed to engender.
2. Last week I mentioned the Yalkut that learns from Moshe’s tefilah of va’eschanan that one should pray even in a time of tzarah and I quoted as hesber from the Chasam Sofer as to why davka this incident is the source for that idea. The sefer Dudai Reuvain from R’ Reuvain Katz has a simpler explanation. Chazal tell us that Moshe Rabeinu davened 515 tefilos to be able to enter Eretz Yisrael. At that point Hashem commanded him to stop praying because he did not want to let him go. Why did Hashem need to command Moshe to stop? Just like Hashem did not respond to the first 515 tefilos, he could not ignore the 516th as well?!
We from here, writes R’ Katz, the tremendous power of tefilah. Even though Hashem had made a gezeirah, had Moshe been able to keep davening, he would have gotten his way. Tefilah is not a mystical reward that Hashem gives out if and when he chooses – it’s a metizyus built into reality. When you daven as much as necessary, it elicits a response. That’s the unique lesson of our parsha that the Yalkut is teaching us.