Commento su Ma'aser Sheni 2:7

לא יעשה אדם סלעיו דינרי זהב – Silver Selahs that he has from Second Tithe monies, he should not make into golden denars, lest he delay their being brought up [to Jerusalem] until he can exchange his Selahs and will be interrupted from going up [to Jerusalem] for the Festival. But the School of Hillel holds that we do not make this decree.

Bet Shammai says: one may not turn his selas into gold dinars. According to Bet Shammai, if one has gathered together a large amount of silver coins of maaser sheni, coins which he used to redeem his produce, he should not exchange them for gold dinars in order to lighten the load that he has to bring to Jerusalem. According to the Talmud, Bet Shammai does not allow this because they are concerned that if this were allowed, people would delay bringing their silver coins to Jerusalem until they had gathered enough to turn them into gold dinars. Delaying bringing coins to Jerusalem might be problematic if this would lead to one accidentally uses them for a profane purpose.

But Bet Hillel permits it. Rabbi Akiva said: For Rabban Gamaliel and Rabbi Joshua I turned silver into gold dinars. Bet Hillel is not concerned with this problem, and neither are Rabbi Akiva, Rabban Gamaliel or Rabbi Joshua. It is interesting to see Rabbi Akiva “serving” his elders. This would have been common for young scholars, who served as apprentices for their teachers.