An old job similar to that of a modern banker. A money changer would change money from one country into money from another country. They would also exchange small coins for larger coins or the other way around. Money changers charged a fee for this work.
Standard coins only started being used around 700 BC. Before that, people weighted pieces of silver to pay for things (Genesis 20:16; 37:28; Judges 17:2). Once standard coins started being used in Asia Minor, other places copied the idea. Coins were different in each country, so money changers had to figure out how much they were worth.
In earlier periods, pieces of silver were weighed out in payment for goods (Genesis 20:16; 37:28; Judges 17:2). Once the standardized coin was adopted in Asia Minor the idea was copied in other lands, but since coins differed from country to country, equivalents had to be worked out by the money changers.
This was very important in Palestine. Every adult Jewish man had to pay a half-shekel tax (Exodus 30:11–16). Jews from different countries might bring many types of coins. The temple leaders had to decide which coin was right for this tax. They chose the silver half-shekel coin from Tyre also known as the tetradrachma.
In Matthew 17:27, Peter was told to pay the temple tax for Jesus and himself with the coin he found in the mouth of a fish. The Mishnah says (Sheqalim 1:3) that money changers worked in local areas on the 15th day of Adar to collect this tax. This was the month before the Passover. Ten days before the Passover the money changers moved to the temple courts to help Jews from other countries.
Jesus met the money changers in the temple courtyard when he “cleaned the temple” (Matthew 21:12–13; Mark 11:15–16; Luke 19:45–46; John 2:13–22). People have argued about why he did this. People needed to get the half-shekels to pay their taxes. They also needed to buy birds, animals, or cakes for offerings. All this buying and money changing seemed wrong in the holy temple area (compare Mark 11:16). Jesus seemed to agree with paying the temple tax itself (Matthew 8:4; 17:24–26; Mark 1:44; Luke 5:14).
It is also possible the money changers and people selling birds and animals were charging too much. The money changers and temple leaders may have done this for their own gain. These activities could have happened farther from the holy area. The noise and bargaining common in markets might have bothered people praying and making offerings in the temple courts. (compare Jeremiah 7:11).