LEAVEN

A substance added to dough or liquids to cause fermentation, especially a portion of fermenting dough preserved for baking purposes. This type of leavening agent is specified by the Hebrew word seʼorʹ (“sourdough”; Ex 12:15) and by the Greek word zyʹme (“leaven”; Lu 13:21). A leavened thing is designated by the Hebrew word cha·metsʹ.​—Le 2:11.

The early Egyptians made beer, which requires a leavening agent for its production, and they baked both leavened and unleavened bread. The Hebrews were likely familiar with “wheat beer.” (Isa 1:22; Ho 4:18, NW; Lexicon in Veteris Testamenti Libros, by L. Koehler and W. Baumgartner, Leiden, 1958, p. 646) Wild yeast that might be obtained from the spores of certain fungus growths may have served as one of the leavening agents for these products. Excavations in Egypt have yielded porous bread containing dead yeast cells. The Egyptians are also said to have used natron (sodium carbonate) in making bread. Sodium carbonate would not bring about the process of fermentation as did sourdough, but it would provide gas bubbles to make the bread rise. In Egypt, as in Israel, the primary practice in breadmaking seems to have been to save some dough from a batch, let it ferment, and use the resulting sourdough to leaven a fresh batch.

In God’s Law to Israel. No grain offering that the Israelites presented by fire to Jehovah was to be made of “a leavened thing.” (Le 2:11) However, leaven could be used in connection with thanksgiving communion offerings, in which the offerer voluntarily made the presentation in a spirit of thankfulness for Jehovah’s many blessings. The meal was to be one of cheerfulness; leavened bread was normally eaten on happy occasions. Along with the meat (that is, the animal) offered, and the unfermented cakes, he would bring ring-shaped cakes of leavened bread, which were not put on the altar but were eaten by the offerer and by the officiating priest.​—Le 7:11-15.

At the presentation of the firstfruits of the wheat harvest, on the day of Pentecost, the high priest waved before Jehovah two loaves of leavened wheat bread. (Le 23:15-21)