Leaven /(?)/

1. Any substance that produces, or is designed to produce, fermentation, as in dough or liquids; esp., a portion of fermenting dough, which, mixed with a larger quantity of dough, produces a general change in the mass, and renders it light; yeast; barm.
2. Anything which makes a general assimilating (especially a corrupting) change in the mass.

   Beware of the leaven of the Pharisees, which is hypocrisy.

imp. & p. p. Leavened; p. pr. & vb. n. Leavening

1. To make light by the action of leaven; to cause to ferment.

   A little leaven leaveneth the whole lump.

2. To imbue; to infect; to vitiate.

   With these and the like deceivable doctrines, he leavens also his prayer.