סוֹר, (= סאור, v. סִיאוּר) fermentation, froth, leaven; trnsf. (cmp. שְׂאוֹר, עִיסָה a. חָמַץ) germ, original nature, character. Snh. 92ᵇ סו̇רו̇ his haughty nature; [oth. opin.: its (the kiln’s) froth], v. מָקַק a. מָרַק. Kidd. 82ᵃ כל שעסקיו סורו רע … he who has a business which brings him in contact with women, has bad leaven in him (or else he would not have chosen such a trade). Hor. 13ᵃ מפני שסוֹרָן רע because they (the mice) are of a mischievous nature. B. Mets. 59ᵇ the Torah cautions repeatedly against ill-treating the proselyte (גֵּר), מפני שסורו רע because his original character is bad (into which ill treatment might cause him to relapse). Kidd. 17ᵇ שמא יחזור לסורו lest he (the proselyte) relapse &c., v. קִילְקוּל. Gen. R. s. 70 היה חוזר לסורו he (Aquila) might have gone back to his evil ways (to heathenism); v. סִיאוּר. Gen. R. s. 74, end (expl. למקומו, Gen. XXXII, 1) לסורו to his evil manners (sensual pleasures). Cant. R. to II, 5; a. e.—Pl. סוֹרִים degenerate, bad people. Num. R. s. 3 אפי׳ סוֹרֵיהֶן וכ׳ even the bad among them are charitable; (Midr. Till. to Ps. XCII בּוֹרִים שבהם).