If a canal passes through a courtyard, we may not draw [water] from it on the Sab-bath, unless they made it a partition ten fists high at the inlet and at the outlet. R’ Yehudah says: The wall over it is considered a partition. Said R’ Yehudah: It happened that [there was] a canal in Avel from which they drew [water] on the Sab-bath upon the ruling of the Sages. They answered him: Because it did not have the minimum dimensions.