“ Half of the second chapter deals with different ways of recital (e.g. reading the parts of the Shema out of order.) The rest of the second chapter and the third deal with exceptions to certain rules regarding Jewish practice on different occasions. The fourth chapter deals with the Shemone Esrei, the main Jewish prayer, and various rules concerning it, like what time can one recite it. An exception is the second mishnah, which talks about a prayer that a certain Tanna (Jewish sage living between 70 to 200 CE) would recite on entering the Beit Midrash (Jewish place of learning) . ”