Rabbi Chanina says: Greater is one who is commanded to do a mitzva and performs it than one who is not commanded to do a mitzva and performs it. (this gemara is also on kiddushin 31a)
But what reward is there for someone who was not commanded to do the mitzvois and what does he achieve by fulfilling them?
someone, Melbourne Australia
You are asking an interesting question. You are starting with the assumption that reward is compensation for something you were asked to do. If you weren't asked to do it, why should you be compensated? If I didn't ask you to mow my lawn and you mow it, why should I pay you? The funny thing is that, in fact, I do actually have to pay you for mowing my lawn because I benefit from it being mowed.
The Shulchan Aruch (Choshen Mishpat 375:1) says that if someone plants fruit trees on your property without your consent, you have to compensate him at some level because you benefited from the new trees (we won't get into the details of how much you have to pay). It may be counterintuitive in today's world, but it shows that one does not have to be asked to do something to have a claim for being compensated. By extension, we may suggest that even if someone is not commanded to do a Mitzvah, Hash-m would still reward him at some level, because He "benefited" from the Mitzvah being done.
Two more points on the subject:
Rav Yosef, in the Gemara you quote from Kidushin, says that common sense dictates that a person who is not commanded to do a Mitzvah should get more reward than one who is commanded, because he didn't have to do it and did it anyway. So you see that it actually makes more sense to be rewarded when not commanded than when commanded.
The Mishnah in Pirkei Avos (2:1) says, "Ki Ein Atah Yode'a Matan Secharan Shel Mitzvos." Why the word "Matan"? Wouldn't it be enough to stay "Ki Ein Atah Yode'a Secharan..." -- "you don't know the reward for Mitzvos"? One answer is that the reward for Mitzvos is, in the final analysis, a gift; it is not something which we are entitled to. We are so heavily indebted to Hash-m for our lives and everything we have that we can't make demands from Him for doing his Mitzvos. Therefore, reward doesn't necessarily follow the rules for workers' compensation.
Kol Tuv,
Yonasan Sigler
Your answer is based on the assumption that Hash-m benefits from the mitzvois. This is however very much flawed - see Iyov perek lamed hey, pessukim 6 and 7. The reason for our doing mitzvois (even though to some extent as the passuk says, it changes nothing) is that since Hash-m chose (for a reason we cannot understand) for there to be a world and for there to be Yidden and He chose to care if we do a mitzvah, thus we must do mitzvois. However, if Hash-m did not command us to do it then we seemingly are not fulfilling his desire and thus accomplish nothing at all.
Dear Sam,
Perhaps just as Hash-m "chose to care if we do a Mitzvah," He also chose to get benefit from our doing them. The Mishnah in Pirkei Avos (2:21) says, "Lo Aleicha ha'Melachah Ligmor v'Lo Atah Ben Chorin l'Hibatel Mimenah" (we are not required to complete the job but neither are we free to abstain from working). It sounds like the Tana of the Mishnah is saying that Jews throughout history (probably starting with Avraham) have been working on a big work project that is leading toward some goal and that each of our Mitzvos accomplishes something toward that goal. In the Kabalah, our Mitzvos and Tefilos are called Tikunim -- rectifications. Our Mitzvos somehow rectify an imperfect world. And us rectifying this world seems to give Hash-m pleasure as we see from a beautiful Midrash (Sefer Heichalos, quoted by the Mishnah Berurah OC 125:5): "Ki Ein Li Hana'ah ba'Olam k'Osah Sha'ah she'Eineihem Nesu'os b'Einai" (Hash-m, as it were, says He has no greater pleasure in this world than when we look up to the Heavens during the recitation of Kedushah).
Kol Tuv,
Yonasan