MONEY-CHANGERS is the RSV rendering of kollybistēs; the nearly synonymous term kermatistēs it trs. as “changer of money”; a related designation, trapezitēs, it gives as “exchanger.” The first of these, kollybistēs, is derived from kollybos, “copper coin,” the regular term for the fee received by the moneychanger for his services. Kollybistēs in its pl. form occurs in Matthew 21:12 and its parallel in Mark 11:15, where Jesus “overturned the tables of the money-changers.” A similar episode in John 2:15 uses this same word, along with kermatistēs in v. 14. The latter word is derived from kerma, “small change” or “coin.” The function of these money-changers was to convert the currency of a worshiper at the Jerusalem Temple into a type of money acceptable for purposes of a sacrificial offering. Since there was no Jewish currency in silver (there apparently had never been any such minted even back in Hasmonean times), ecclesiastical approval had for some reason been granted to the Tyrian half-shekel or didrachma, and the shekel or tetradrachma (even though they bore the effigy of Baal Melkart, the patron god of Tyre) as acceptable for the Temple poll tax, which amounted to a yearly levy of one half shekel per male citizen. (Cf. the episode in Matt 17:27, where Peter is told to use the shekel he had found in the mouth of the fish he had caught, in order to pay the temple tax for himself and for Jesus.) It may have been necessary for smaller offerings to be converted into acceptable bronze coinage, such as the lepta or “mites” minted by the Jewish rulers of the Hasmonean dynasty. At any rate, granted the legitimacy of this taboo against pagan currency as a medium for sacrifice (in place of clean animals sacrificed on the altar), the money-changer seems to have performed a useful function. It could not have been because of anything inherently reproachful in their activity that they aroused Christ’s ire in the Temple. Undoubtedly they served the convenience of the public, esp. where birds, animals, or cake-offerings had to be purchased by city dwellers not possessing livestock of their own. In these transactions it must have been necessary to make small change available if the buyer was not to be cheated, and of course the banker who provided this service was entitled to some sort of a fee, in order to make a living.
There seem to be only two possible grounds on which they incurred our Lord’s indignation: either their charges for money-changing were excessive and tended to gouge the poor and pious, or else they had their tables set up so close to the section of the Temple set apart for worship and sacrifice as to interfere with these sacred functions. On either count, or on both counts, Christ could have leveled the charge of turning the house of God into “a den of thieves.” It is quite conceivable that the loud and passionate haggling that undoubtedly accompanied this activity of changing money in an Oriental setting was completely disturbing to genuine devotion; and when this commotion was augmented by the lowing of cattle, the bleating of sheep and goats, and the cooing of pigeons and doves, the resulting hubbub must have made devotional exercises most difficult for the sincere worshiper. At any rate, Jesus found it necessary to clear them all out, and thus relegate them to a suitable distance from the place of sacrifice and prayer.
International Standard Bible Encyclopedia (1915)
(kollubistes, from kollubos, "a small coin," so "a money-changer," or "banker" (Mt 21:12; Mr 11:15; "changers" in Joh 2:15; compare Joh 2:14, where kermatistes, "a dealer in small bits," or "change," is also rendered "changers"); compare trapezites, "one who sits at a table," "a money-changer," "a banker" or "broker"; one who both exchanges money for a small fee and pays interest on deposits (Mt 25:27, the King James Version "exchangers," the American Standard Revised Version "bankers")): The profession of money-changer in Palestine was made necessary by the law requiring every male Israelite who had reached the age of 20 years to pay into the treasury of the sanctuary a half-shekel at every numbering of the people, an offering to Yahweh, not even the poor being exempt. It seems to have become an annual tax, and was to be paid in the regular Jewish half-shekel (Ex 30:11-15). Since the Jews, coming up to the feasts, would need to exchange the various coins in common circulation for this Jewish piece, there were money-changers who exacted a premium for the exchange. This fee was a kollubos (about 31 cents in U.S. money, i.e. in 1915), hence, the name kollubistes. The Jews of Christ’s day came from many parts of the world, and the business of exchanging foreign coins for various purposes became a lucrative one, the exchangers exacting whatever fee they might. Because of their greed and impiety, Jesus drove them from the courts of the temple.