BT Ber 27b(8) :מי בדלת א׳ל אין בדילנא ולא א׳ל מי בדיל מר‏ : are you abstaining (from work)? He said: "Yes, I am abstaining." And he did not say to him: "Is the master abstaining?"
See the entire entry for bdl vb. to keep separate