Bava Metzia

Whatever is assessed as the value of another object,  as soon as one party takes possession thereof, the other assumes liability for what is given in exchange. Reason too supports this — For the second clause teaches: How so? If one bartered an ox for a cow, or an ass for an ox. This proves it. Now, on the original hypothesis that coin [is referred to], what is meant by 'How so?'  — 'It means this: And produce  too can effect a barter. How so? If one bartered an ox for a cow, or an ass for an ox. Now, that is well on the view of R. Shesheth, who maintained that produce can be employed for barter. But according to R. Nahman, who said: Only a utensil, but not produce, can effect a barter, what is meant by 'How so'?-It means this: Money sometimes ranks as [an object of] barter. How so? If one bartered the money of an ox for a cow, or the money of an ass for an ox.  What is R. Nahman's reason?  He agrees with R. Johanan, who said: Biblically Speaking, [the delivery of] money effects a title. Why then was it said that only meshikah gives possession? As a precautionary measure, lest he say to him, 'Your wheat was burnt in the loft.'  Now, the Rabbis enacted a preventive measure only for a usual occurrence, but not for an unusual occurrence.  Now, according to Resh Lakish, who maintains that meshikah is explicitly required by Biblical law: it is well if he agrees with R. Shesheth: then he can explain  it as R. Shesheth. But if he holds with R. Nahman, that produce cannot effect a barter, whilst money does not effect a title [at all], how can he explain it? — You are forced to assume that he explains it as R. Shesheth. We learnt: ALL MOVABLES ACQUIRE EACH OTHER, whereon Resh Lakish said: Even a purse full of money [when bartered] for a purse full of money. — R. Aha interpreted it as referring to the Bithynian and Ancyrean  denarii, one of which was cancelled by the State, and one by local authorities.  And both are necessary. For if we were taught this of State cancellation,  that is because such coins have no [official] currency at all; but in the case of local repeal, since these coins circulate in another province, I might regard them as money, which cannot be acquired through barter. Whilst if it were stated in connection with local repeal, that is because they have neither a secret nor an open circulation [within that province]; but when cancelled by the State, since they circulate clandestinely, I might still regard them as coin, which cannot be acquired through barter. Thus both are necessary. Rabbah said in R. Huna's name: [If A said to B,] 'Sell [it] me for these [coins],' he acquires title thereto,