Midrasch zu Schemuel I 22:18

(I Sam. 15, 5) And he (Saul) quarreled in the valley, etc. R. Mani explained this to mean that he (Saul) had a quarrel concerning the valley; i.e., when the Holy One, praised be He! said unto Saul (Ib. ib., 3) Go and smite Amaiek, Saul [began to argue and] said: "If for the sake of one soul [that is murdered] the Torah ordered a heifer to be brought in to a wild valley where its neck should be broken [as atonement for the murder], how much more shall I have to suffer for so many souls [should I murder them]? And again, if man sinned, why are the beasts to blame [that I should destroy them also]? And again, if adults sinned, why are the little ones to blame [that I should destroy them also]?" Immediately thereupon, a Bath-Kol went forth and said unto him (Ecc. 7, 16) Be not righteous over much. Later, when Saul gave Doeg the order (I Sam. 22, 18), Turn thou round, and fall upon the priest and kill both men and women; another BathKol went forth and said unto him (Ecc. 7, 17) "Be not wicked over much."