Our Gemara on Amud Aleph discusses a valuable moral principle: “A person should not pour the leftover water from his well when others are in need of it.”. In our Gemara’s case, it refers to a situation where there are two co-wives and one can do chalitza to either. If one of them is already invalid for marriage to a cohen, he should choose to do chalitza to her. Thus, the other widow could have a chance to marry a cohen in the future.

Tosafos Rid (Yevamos 44a) asks why does this Gemara consider this moral idea to be novel and derived from this teaching. Does it not fall under the general prohibition to not behave as sodomites? There is an already existing halakhic requirement that one may not withhold a benefit from another person if it does not incur any additional cost to you.which is known as middas Sodom. (See for example Shulkhan Arukh Choshen Mishpat 153:8 and 154:3, and Orach Chayyim 386:9.) Tosafos Rid Answers that this case has an additional factor that we might not have considered Middas Sodom. Here, at the moment, there is no real person losing out. Theoretically, she might meet a nice cohen in the future whom she will want to marry. But right now, he does not exist and she may never meet him. Unlike the classic Choshen Mishpat cases of Middas Sodom, where someone right now is losing a benefit, in this case it is only a potential future loss.

Once we are discussing this principle of not wasting another person’s future benefit and spilling the well water, I will share a modern day application of this principle that I heard years ago from Rav Fishel Shechter’s Daf Yomi recordings. In especially congested parking areas like Brooklyn, you often have space for two cars on the length of street that is between two driveways. However it takes a little time and concentration to line up your car so you aren’t blocking the driveway in front or back of your car, and make room for another car. It is much easier to just pull into the space and leave a few feet in front and in back, and shoyn, you’re parked ! But Rav Shechter suggested this is a violation of לא ישפוך מי בורו because with a small effort you can make room for another car to park. And based on the Tosafos Rid we just saw, it doesn’t matter that no one right now is looking for the spot, because the potential in the future is likely.