We learned in the Mishna (24b) that there are areas of halakha where the rules regarding teruma (tithes) are more stringent than those dealing with kodashim (Temple sacrifices). The example brought is that a simple farmer (referred to as an am ha’aretz) could be trusted to say that the wine or oil that he produced was guarded to be sure that it remained tahor (ritually pure) if it was made with the intention of offering the wine as a libation on the altar or as part of the grain offering. If, however, the am ha’aretz offered a kohen wine or oil as teruma, he could not be trusted.
The Mishna mentions that our willingness to believe an am ha’aretz regarding kodashim is limited to Yehuda – the southern part of the Land of Israel – but apparently it does not apply to the Galil – the northern part of the country. Reish Lakish explains that this is based on a technicality – that the Jewish community in the Galilee is separated from the Temple in Jerusalem by an area that was entirely populated by Kutim, and that area was considered to be intrinsically tameh (ritually defiled) given its status as eretz ha-amim (land inhabited by non-Jewish nations).
The Kutim, or Shomronim (Samaritans), were centered in the city of Shomron, not far from the city of Shekhem. This was not a political boundary, and the area in which a large population of Kutim lived shifted over the generations. During the period of the Hasmoneans it was a very small area, but at other times it widened to the extent that there was a strip running from the Mediterranean to the Jordan River, effectively dividing the Jewish population into two – Yehuda and the Galil – with no territorial connection between them. Once the Sages ruled that the Kutim were to be considered non-Jews, a situation was created where part of the territory of the Land of Israel was considered to be eretz ha-amim, thus the only way to transport items from the Galilee to the Temple in a state of tahara would have been by crossing the Jordan.
According to some, this created a situation whereby Jews living in the Galilee were forced to travel to Jerusalem a week before the holidays in order to give them time to purify themselves after their journey through eretz ha-amim.