Leaven
Leaven , noun
[Old English levain, levein, French levain, Latin levamen alleviation, mitigation; but taken in the sense of, a raising, that which raises, from levare to raise. See Lever, n.]
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.
Leaven , transitive verb
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.