Leaven @ (1.) Heb. seor Exodus:12:15Exodus:12:19Exodus:13:7; Leviticus:2:11), the remnant of dough from the preceding baking which had fermented and become acid. (2.) Heb. hamets, properly "ferment." In Numbers:6:3, "vinegar of wine" is more correctly "fermented wine." In Exodus:13:7, the proper rendering would be, "Unfermented things [Heb. matstsoth] shall be consumed during the seven days; and there shall not be seen with thee fermented things [hamets], and there shall not be seen with thee leavened mass [seor] in all thy borders." The chemical definition of ferment or yeast is "a substance in a state of putrefaction, the atoms of which are in a continual motion." The use of leaven was strictly forbidden in all offerings made to the Lord by fire Leviticus:2:11Leviticus:7:12Leviticus:8:2 ; Numbers:6:15). Its secretly penetrating and diffusive power is referred to in 1Corinthians:5:6. In this respect it is used to illustrate the growth of the kingdom of heaven both in the individual heart and in the world Matthew:13:33). It is a figure also of corruptness and of perverseness of heart and life Matthew:16:6Matthew:16:11Mark:8:15; 1Corinthians:5:7-8).