Manna. Manna, sometimes or archaically spelled mana is, according to the Bible, an edible substance which God provided for the Israelites during their travels in the desert during the forty-year period following the Exodus and prior to the conquest of Canaan. It is also mentioned in the Quran three times. In the Hebrew Bible, manna is described twice: once in Exodus 16:1-36 with the full narrative surrounding it, and once again in Numbers 11:1-9 as a part of a separate narrative. In the description in the Book of Exodus, manna is described as being a fine, flake-like thing like the frost on the ground. It is described in the Book of Numbers as arriving with the dew during the night. Exodus adds that manna was comparable to hoarfrost in color, and similarly had to be collected before it was melted by the heat of the sun, and was like a coriander seed in size but white in color. Numbers describes it as having the appearance of bdellium, adding that the Israelites ground it and pounded it into cakes, which were then baked, resulting in something that tasted like cakes baked with oil. Exodus states that raw manna tasted like wafers that had been made with honey. The Israelites were instructed to eat only the manna they had gathered for each day. Stored manna bred worms and stank: the exception being that stored the day before the Sabbath, when twice the amount of manna was gathered. This manna did not spoil overnight. Exodus 16:23-24 states: This is what the Lord commanded: Tomorrow is to be a day of rest, a holy Sabbath to the Lord. So bake what you want to bake and boil what you want to boil. Save whatever is left and keep it until morning. So they saved it until morning, as Moses commanded, and it did not stink or get maggots in it. In the Bread of Life Discourse in John's Gospel, the evangelist refers three times to the manna which the Jews' ancestors ate in the desert: the Jews refer to the manna given to them by Moses as a sign of God's promised covenant, and Jesus asserts that the manna was from God and not from Moses, and that the people who ate it were nourished on their journey but ultimately died. In contrast, according to the gospel, Jesus offered living bread, and whoever ate this bread would never die. It is narrated in the hadith collection Sahih Muslim that the Prophet Muhammad said Truffles are part of the 'manna' which Allah sent to the people of Israel through Moses, and its juice is a medicine for the eye. Some scholars have proposed that manna is cognate with the Egyptian term mennu, which designated a substance that figured in offerings. At the turn of the twentieth century, Arabs of the Sinai Peninsula were selling resin from the tamarisk tree as man es-simma, roughly meaningheavenly manna. Tamarisk trees were once comparatively extensive throughout the southern Sinai, and their resin is similar to wax, melts in the sun, is sweet and aromatic, and has a dirty-yellow color, fitting somewhat with the biblical descriptions of manna. However, this resin is mostly composed of sugar, so it would be unlikely to provide sufficient nutrition for a population to survive over long periods of time, and it would be very difficult for it to have been compacted into cakes. Other researchers have believed manna to be a form of lichen; a plant colony that often has a low mass per unit volume density and a large sail area. In particular, Lecanora esculenta has been postulated. Known natural aerial falls of various lichens have been described as occurring in accounts separate from that in the Bible. In some parts of Asia Lecanora esculenta covers the soil to such a degree that, according to Parrot, it forms beds 15 to 20 centimetres thick. In the biblical account, the name manna is said to derive from the question man hu, seemingly meaning What is it?; this is perhaps an Aramaic etymology, not a Hebrew one. Man is possibly cognate with the Arabic term man, meaning plant lice, with man hu thus meaning this is plant lice, which fits one widespread modern identification of manna, the crystallized honeydew of certain scale insects. In the environment of a desert, such honeydew rapidly dries due to evaporation of its water content, becoming a sticky solid, and later turning whitish, yellowish, or brownish; honeydew of this form is considered a delicacy in the Middle East and is a good source of carbohydrates. In particular, there is a scale insect that feeds on tamarisk, the Tamarisk manna scale, which is often considered to be the prime candidate for biblical manna.