Where does the obligation to say grace after meals — Birkat HaMazon — come from? The Mekhilta traces it to a single verse: (Deuteronomy 8:10), "And you shall eat and you shall be sated, and you shall bless the Lord your God for the good land which He gave you."
The rabbis broke this verse into four distinct phrases, each corresponding to one of the four blessings of the grace after meals. "And you shall eat and you shall be sated" — this is the first blessing, thanking God for providing food. "For the land" — this is the second blessing, giving thanks for the land of Israel. "The good" — this corresponds to the third blessing, "who builds Jerusalem," as confirmed by (Deuteronomy 3:25), which describes "the good land and the Lebanon" (Lebanon being a rabbinic code name for the Temple). "That He gave you" — this is the fourth blessing, "who is good and does good," acknowledging that God gave all good things to Israel.
This derivation is remarkable for its economy. A single verse of Torah, when read with sufficient precision, yields the entire structure of one of Judaism's most frequently recited prayers. Every word carries the weight of a separate blessing. The rabbis did not invent the grace after meals and then search for a proof text. They found the prayer already embedded in the Torah's own language, waiting to be unpacked by careful readers. Four phrases, four blessings — a complete liturgy hiding in plain sight within a single line of Scripture.