출애굽기 16:35의 주석

ארבעים שנה FORTY YEARS — But was not this period short of thirty days, since it was on the sixteenth of Iyar that the Manna fell for them for the first time and on the fifteenth of Nisan that it ceased, as it is said, (Joshua 5:12) “And the Manna ceased on the morrow”? (cf. the preceding verse which speaks of the day when they ate unleavened bread). But this tells us that in the cakes that Israel had brought out of Egypt and which they ate from the 15th of Nisan to the 16th of Iyar after they left Egypt they experienced the taste of Manna (so that the 40 years mentioned here as those during which they ate Manna may be regarded as complete) (Kiddushin 38a).

אכלו את המן, in lieu of bread made from wheat or other cereals. The Israelites themselves testified to this in Numbers 11,6 when they said (complainingly) בלתי אל המן עינינו, “all we have to look at is the manna.”

את המן אכלו ארבעים שנה, they ate the manna for forty years. There is a good reason why the Torah refers twice to the Israelites eating manna for forty years. Once the people entered the Holy Land they ate manna which had been stored in their vessels, whereas up to the time they crossed the river Jordan they ate manna which had come from heaven on that same day. We have no difficulty in understanding that the longer something of celestial origin remains in our atmosphere, our domain, the more terrestrial it became in nature. The Torah therefore was forced to mention that the manna which the Israelites ate in the desert was in a class by itself. In Kidushin 38 the Talmud asks: "how can the Torah speak about the Israelites eating manna for forty years? They did not receive the first portion of manna until 30 days after the Exodus! The answer given is that their cakes (the unleavened bread they took out of Egypt) tasted like manna.