Why does Rashi give a different answer to 2 mishnaios which deal with the same outcome. In the first mishna on top of amud ,Rashi said reason why one should not change all silver back to copper in Yerushalaim is that it will generate a hudge amount of copper that will be lacking and consequently copper will roise in price. But Rashi didn't give this reason when the next mishna that deals with someone changing silver to copper in yerushalaim. Why? Why did he give a totally different reason even though the reason he gave in this last mishna is valid.
michel bitton, montreal, canada
1. The difference is that the first Mishnah refers to someone changing copper into silver coins outside Yerushalayim whilst the second Mishnah refers to someone changing silver into copper inside Yerushalayim.
2. Beis Shamai maintains that if one possesses a lot of copper coins before his journey to Yerushalayim, he should not change them all into silver coins. We do not want everyone to arrive in Yerushalayim only with silver coins because if they do, then at the beginning of the Yom Tov there will be a great demand for copper coins since it is only with these lower denomination coins that one can make small food purchases. The demand on copper will push the price up and Ma'aser Sheni will suffer a loss. Therefore, Beis Shamai says that one should retain one half of his copper coins outside of Yerushalayim and buy a silver coin with the other half. Consequently, at the beginning of everyone's stay in Yerushalayim the visitors will own enough copper coins. They will only start gradually converting the silver coins into copper coins about half way through the visit. Since there will be no sudden rush for copper, the price will not rocket up.
3. The second Mishnah refers to someone who possesses a silver coin inside Yerushalayim during his visit there. We tell him not to convert it all into copper. Even though one might say that in Yerushalayim one needs smaller copper coins with which to buy food, nevertheless we are apprehensive that he might not stay here long enough and will be left with too many copper coins at the end of his visit. He might deposit these coins with an resident of Yerushalayim until he returns at the next Yom Tov and in the meantime the coins will rust or become moldy.
4. In short, the first Mishnah ensures that there will be enough copper coins in town at the beginning of Yom Tov, while the second Mishnah ensures that not too many copper coins will be left over at the end of Yom Tov.