When the Torah says that Yithro "rejoiced over all the good" that God had done for Israel (Exodus 18:9), the rabbis asked a natural question: which specific good was Yithro rejoicing about? The answer, according to R. Yehoshua, was the manna — that miraculous bread from heaven that sustained the Israelites in the wilderness.
But the manna was not ordinary bread. The Mekhilta records an astonishing claim about what the Israelites experienced when they ate it. They said: "In this manna that the Lord has given us, we savor the taste of the loaf, of flesh, of fish, of hoppers, of all the delicacies in the world." The manna was not one flavor. It was every flavor. Whatever you wanted to taste, the manna became that food in your mouth.
R. Yehoshua grounded this interpretation in the careful phrasing of the verse itself. The text does not simply say Yithro rejoiced over "good." It builds in four stages: "good," "the good," "all the good," "over all the good." Each additional word expands the scope of what Yithro was celebrating. A single food that contained within it every possible taste — that is not merely good. That is all the good, the totality of culinary delight compressed into one heavenly substance.
This is what made Yithro's joy so complete. He was hearing about a God who did not merely feed His people, but who fed them everything at once.