Midrasch zu Jeschijahu 30:31

(Fol. 32) R. Shephatia said again in the name of R. Jochanan: "Whence do we know that we may avail ourselves of a Heavenly voice? It is said (Is. 30, 31) Thine ears shall hear a thing from behind them, saying. When is this true? When one perceives a male voice in town, and a female voice in the country, and also when it says: 'Yea, yea,' or 'Nay, nay' [in double]." Another thing said R. Shephatia in the name of R. Jochanan: "Whoever reads without sweetness, and chants while reading Talmudic lessons, of him says the verse (Ezek. 20, 25) And I also have given unto them laws that are not good and ordinances whereby they could not live." R. Mesharshia raised the following objection: "Shall I say because one cannot sweeten his voice, ordinances whereby they could not live should be applied to him?" Therefore we must say that it refers to what R. Mesharshia said: "If two scholars are in one town, and derive no pleasure in discussing Halacha, to the passage. And ordinances whereby they could not live is applied."