a little leaven ferments the whole lump of dough

ζύμη, ης, ἡ (‘yeast, leaven’ Aristot., Gen. An. 3, 4, 755a, 18ff; Plut., Mor. 289f; PTebt 375, 27; LXX; Philo, Spec. Leg. 1, 291; 2, 182; Jos., Ant. 3, 252; Just., D. 14, 3; cp. 14, 2 [1 Cor 5:8?])

① fermented dough, leaven (the rendering ‘yeast’ [as NRSV gener., REB Mt 13:33, Lk 13:21] popularly suggests a product foreign to ancient baking practice), lit. Mt 13:33; Lk 13:21. More fully ζ. τῶν ἄρτων Mt 16:12. μικρὰ ζύμη ὅλον τὸ φύραμα ζυμοῖ a little leaven ferments the whole lump of dough 1 Cor 5:6 (Cyranides p. 64, 22 μετὰ ζύμης μικρᾶς)=Gal 5:9, shown by its repeated use to be a proverbial saying, serves to picture the influence of apparently insignificant factors in the moral and relig. sphere (on neg. aspect s. HBetz, Gal., Hermeneia 266 n. 125).

② that which negatively permeates attitude or behavior, leaven fig. ext. of 1: ζ. is used of the attitudes of Pharisees and of Herod Mk 8:15. Of the pretense of Pharisees Lk 12:1. Of the teaching of Pharisees and Sadducees Mt 16:6, 11. In IMg 10:2 the leaven that has grown old and sour means a life regulated by Judean cultic instruction. It is contrasted w. Jesus Christ, the νέα ζ., ibid. Employing the language of the Passover rules (Ex 12:15, 19; 13:7; Dt 16:3f), Paul admonishes ἐκκαθάρατε τ. παλαιὰν ζ. 1 Cor 5:7 and explains that the old leaven is ζ. κακίας κ. πονηρίας vs. 8 (on problems connected w. the imagery s. Straub 80f).—RAC I 1056–62.—DELG. M-M. EDNT. TW.