We learn in a mishnah:
In the case of a pit that the first person who passed by covered after using it, and then the second came to use it and found it uncovered, and he did not cover it, the second one is liable.
Rachel makes use of a pit and then covers it, as required. Later, Leah comes to use the pit and finds it uncovered. When she is done, she leaves it the way she found it — uncovered. According to the mishnah, Leah is liable for future damage caused by the uncovered pit.
The mishnah’s ruling makes a certain amount of sense. The fact that something happened to the covering that Rachel placed over the pit before Leah arrived does not relieve Leah of her responsibility to secure the pit after she is done using it.
That is, until the Gemara takes up the matter.
And until when is the first person (i.e. Rachel) exempt?
The Gemara is not so quick to let Rachel completely off the hook. True, Leah bears responsibility for leaving the pit in a dangerous state, but so does Rachel. Although she did cover the pit before she left, she did not do so adequately, as is evident in the fact that by the time Leah showed up the cover was no longer there.
So at what point does the Gemara assign Rachel responsibility? It depends who you ask:
Rav says: Until she becomes aware that the pit became uncovered.
And Shmuel says: She is exempt until others inform her.
And Rabbi Yohanan says: She is exempt until others inform her and she hires workers to cut cedar trees and cover it.
According to Rav, once Rachel returns to the pit and sees that her cover has come off, she resumes responsibility for any future damage. Shmuel says she becomes responsible once others inform her that her cover has failed. And Rabbi Yohanan extends the time to include repairs. All assume that because Rachel covered the pit when she was done with it, she is exempt from liability until she becomes aware that there is a problem.
But this is not the only way to read the Gemara. Some commentators read it as follows:
Rav says: She is exempt for the time necessary for her to become aware that the pit became uncovered.
And Shmuel says: She is exempt for the time necessary for others to inform her.
And Rabbi Yohanan says: She is exempt for the time necessary for others to inform her and she hires workers to cut cedar trees and cover it.
In other words, Rachel does not have to see the pit herself, or to be made aware of the situation — all that has to happen is that enough time has to pass for these things to have taken place.
Though the mishnah apparently places all responsibility for the uncovered pit with Leah, the Gemara says that at certain points Rachel might be the one responsible, even after Leah has left the scene. But what that time frame is depends on how you understand the Gemara.
If I were Rachel, I’d pick the first reading, which limits Rachel’s culpability until she becomes aware that there is a problem — which could be never. If I were Leah, I’d pick the second reading, which has a fixed time frame when responsibility rests on Rachel even if she doesn’t know the pit’s cover is off.
Read all of Bava Kamma 52 on Sefaria.