Yerushalmi Eruvin 8:7 ירושלמי עירובין ח׳:ז׳

MISHNAH: From a water canal²⁰Ten hand-breadths deep and four wide. In general this is a separate karmelit and not part of the courtyard. which crosses a courtyard one does not draw on the Sabbath unless one made a partition ten hand-breadths high at its entrance and exit. Rebbi Jehudah said, it happened that from the water canal of Abel one was drawing water²¹Without separate partitions for every courtyard the canal is crossing. on the instruction of Elders on the Sabbath. They told him, because it did not have the measure²²Not 10 hand-breadths deep and 4 wide..

HALAKHAH: Paragraph⁸¹Discussion of Mishnah 8.. The Mishnah if it is deep ten [hand-breadths] and wide four [hand-breadths]²⁰Ten hand-breadths deep and four wide. In general this is a separate karmelit and not part of the courtyard. and open on both sides. If it is open on one side one puts a beam or a lathe on that side⁸²As S. Liebermann points out, this cannot describe the situation of the Mishnah that a water canal runs through a private domain since beam and lathe are appropriate only for alleys. Therefore one has to assume that the canal at Abel was running in the alleys and the problem is to let the dwellers in an alley draw water on the Sabbath.. If it is open on both sides one puts a beam or a lathe on one side and makes the shape of a door at the other. Do not two different domains use the same domain⁸³If the canal is wide and deep enough to constitute a karmelit domain in itself it would be impossible to make a common eruv for both sides of the street. This in itself should prevent anybody from drawing water on the Sabbath.? Explain it if there were houses on one side⁸⁴The objection is well taken. One has to assume that there were houses only on one side; the other side was bounded either by a solid wall or by uninhabited areas..

The following is obvious: If it is ten deep but not four wide one may move and fill⁸⁵From a canal running through an alley. Any ditch which is not 4 hand-breadths wide at the surface does not interfere with eruvin (Mishnah 7:3).. If it was four wide⁸⁶This is implied by Mishnah 7:3. but not ten deep it is obvious that one may move. May one fill? Rebbi Ḥinena said, it is permitted. Rebbi Mana said, it is forbidden. Our Mishnah disagrees with Rebbi Mana: “They told him, because it did not have the measure.” It was neither ten deep nor four wide⁸⁷Babli 87a.. But if it had been ten deep but not four wide⁸⁸It is obvious that one has to read: if it would not have been ten deep but four wide. it would have been forbidden. Even if it is four wide but not ten deep it is permitted. The case happened as it happened⁸⁹No logical derivations are possible for rules derived from actual happenings since there the conditions are not subject to adjustment..