Midrasch zu Bamidbar 15:17

(Fol. 38) When the daughter of R. Samuel b. Juda died, one of the Rabbis said to Ulla: "Let us go and console him." He said to them: "What have I to do with the consolation of a Babylonian, for it may turn into a blasphemy, as they are in the habit of saying in such cases. What can be done? [against the will of God,] which means that if something could be done against His will they would, [and this is certainly a blasphemy]. He then went alone, and he began his consolation on the following passage: (Deut. 2, 9) And the Lord said unto me. Do not attack the Moabites, nor contend with them in battle. Could it, then, even enter Moses' mind to engage in war without the consent of the Lord. But Moses drew an a fortiori conclusion for himself, saying thust: 'If concerning the Midianites who only came to help the Moabites the Scripture says [Num. 15, 17) Attack the Midianites, and smite them, how much more so should (Ib. b) it be applied to the Moabites themselves?' The Holy One, praised be He! then said: 'Not as it struck your mind, did it strike Mine. Two good doves I have to bring forth from them; namely, Ruth the Moabite, and Naomi the Ammonite.' Now is there not a fortiori conclusion to be drawn? If for two good doves the Holy One, praised be He! has saved two great nations and did not destroy them, how much more so would He have saved the life of the master's daughter if she were to be righteous and something good would have to come forth from her!"