Mishná sur Les Nombres 9:28

Ben Antigonus brought up firstlings from Babylon, but they did not accept from him. Joseph the priest brought first fruits of wine and oil, but they did not accept from him. He also brought up his sons and members of his household to celebrate Pesah katan in Jerusalem, but they turned him back, so that the thing should not become firmly fixed as an obligation. Ariston brought his first fruits from Apamea and they accepted from him, because they said, one who buys [a field] in Syria is as one who buys [a field] in the outskirts of Jerusalem.

A kokhin field may neither be planted nor sown, but its earth is regarded as clean and ovens may be made of it for holy use. Bet Shammai and Bet Hillel agree that it [a bet peras in which a grave was plowed over] is examined for one who wished to perform the pesah sacrifice,but is not examined for one who wants to eat terumah. And as for a nazirite: Bet Shammai say: it is examined, But Bet Hillel say: it is not examined. How does he examine it? He brings earth that he can move, and places it into a sieve with fine meshes, and crumbles. If a bone of barley-corn size is found there [the person passing through the field] is deemed unclean.

A kokhin field may neither be planted nor sown, but its earth is regarded as clean and ovens may be made of it for holy use. Bet Shammai and Bet Hillel agree that it [a bet peras in which a grave was plowed over] is examined for one who wished to perform the pesah sacrifice,but is not examined for one who wants to eat terumah. And as for a nazirite: Bet Shammai say: it is examined, But Bet Hillel say: it is not examined. How does he examine it? He brings earth that he can move, and places it into a sieve with fine meshes, and crumbles. If a bone of barley-corn size is found there [the person passing through the field] is deemed unclean.