The words of Shema contain allusions to a person’s limbs, and reciting it twice a day, morning and evening, is tantamount to sacrificing an offering in the Temple.

Rabbi Mani said: Do not take the reciting of Shema lightly, because it contains 248 words, including the statement: “Blessed is the name…,” and 248 is equal to the number of a person’s limbs.

The Holy One, blessed be He, said: If you observed My 248 words and recited Shema in its proper form, I will protect your 248 limbs.

This is what the Holy One, blessed be He, said to Israel: In the past you would bring an offering to Me twice a day: “The one lamb you shall offer in the morning, and the second lamb you shall offer in the afternoon” (Numbers 28:4). It was revealed and known before Me that the Temple was destined to be destroyed, and from then on you would be unable to sacrifice offerings. But I am asking in exchange for the offerings that you recite Shema Yisrael in the morning and Shema Yisrael in the evening, and it is considered before Me more valuable than all the offerings. (Tanĥuma, Kedoshim; Yalkut Shimoni, Va’ethanan 1:835)