הלכה על ברכות 52:4

That is that He commanded us to read the recitation of Shema in the evening and the morning. And that is His saying, "and you shall speak about them" (Deuteronomy 6:4). And the regulations of this commandment have already been explained in Tractate Berakhot; and there (Berakhot 21a), it is explained that the recitation of Shema is [an obligation] from the Torah. And it is written in the Tosefta (Tosefta Berakhot 3:1), "Just like the Torah established [a set time for] the recitation of Shema, so too did the Sages establish a time for prayer." This means to say that the times of prayer are not from the Torah - though the actual obligation to pray is from the Torah, as we explained (Sefer HaMitzvot, Positive Commandments 5) - and the Sages, may their memory be blessed, arranged times for them. And this is the content of their saying (Berakhot 26b), "They established the prayers corresponding to the daily sacrifices" - meaning, that they fixed their times according to the times of the sacrifices. And women are not obligated in this commandment. (See Parashat Vaetchanan; Mishneh Torah, Reading the Shema 1.)