Gemara

27a (Mishnah): If Reuven left his jug in a Reshus ha'Rabim, and Shimon tripped on it and it broke, Shimon is exempt. If Shimon was hurt, Reuven is liable.

27b - Question: Why is Shimon exempt? He should look where he walks!

Answer #1 (Rav): The case is, Reuven filled the Reshus ha'Rabim with jugs.

Answer #2 (Shmuel): It was dark.

Answer #3 (R. Yochanan): The jug was around a corner, out of his sight.

Question (Rav Papa): According to Rav, why does the Mishnah say 'he tripped'? He should be exempt even if he broke it intentionally!

Answer (Rav Zvid): This is true. The Reisha teaches that if Shimon tripped and was hurt, Reuven must pay. If Shimon intentionally broke it, he damaged himself; Reuven is exempt. Since the Reisha discusses tripping, also the Seifa does.

Answer #4 (R. Aba): Normally, people do not look where they walk.

Cases occurred, and Shmuel and Rava obligated one who tripped to pay.

Suggestion: Rava holds like Shmuel.

Rejection (Rav Papa): Perhaps he holds like R. Aba. He ruled about Kelim left near the corner of the olive-press. Since the owner was allowed to leave his Kelim there (such is the custom), one who walks must watch his step.

28b (Shmuel): One is liable for "an ox" that fell in a pit, but not for a man. This applies only to death. He is liable for damage to a person.

54a (Mishnah): If an ox fell in a pit, if deaf, insane, or a child, the owner is paid.

(R. Yochanan): It means, the ox is deaf, insane or (very) young.

Question: If the ox was healthy, would the pit's owner be exempt?!

Answer (Rava): Yes! The ox should have watched where it is walking.

Support (Beraisa): If an ox is deaf, insane, young, blind or walking at night, the pit owner is liable. If the ox was healthy and fell in during the day, he is exempt.

Rishonim

Rif (12a): We concluded that normally, people do not look where they walk.

Rosh (3:1): Shmuel exempts when it was dark, for he could not look. Man is always Mu'ad, but he is exempt for a big Ones like this. The Rif rules that normally, people do not look where they walk, for Ravina and Rav Ashi hold like this. Also, the Gemara asked incredulously 'does Rava hold like Shmuel?!' This shows that the Halachah is unlike Shmuel. All the more it is unlike R. Yochanan; a corner is a smaller Ones than darkness. Normally, we rule like Shmuel (in monetary matters) and R. Yochanan against Rav. Since the Halachah does not follow Shmuel and R. Yochanan, surely it does not follow Rav. This applies to man, for his eyes are above, and he does not look in front of his feet. However, if a seeing animal fell into a pit during the day, the pit owner is exempt. An ox's eyes are down; it should look where it walks more than a person.

Rambam (Hilchos Nizkei Mamon 12:16): Levi is liable for an animal that died in his pit or struck his mound only if the animal was young, deaf, crazy, blind, or fell at night. If an alert animal fell during the day, Levi is exempt, for this is like Ones. Normally, an animal sees and avoids obstacles. If a person fell in a pit and died, even if he was blind or fell at night, the owner is exempt. If he or an alert animal was damaged, the owner pays full damage.

Rebuttal (Ra'avad): Why is he liable for an alert animal during the day? Why is damage different than death?

Magid Mishneh: The Gemara said that people do not look where they walk. The Rambam holds that all the more so animals, which lack understanding! We exempt an alert animal only regarding death. It should avoid a big pitfall. It does not guard itself from small damages; this is not Ones. Perhaps the Ra'avad holds that people think, therefore they do not look where they walk. The Rashba holds like the Ra'avad.

Rambam (13:5): If Levi left a jug in Reshus ha'Rabim, and David stumbled on it and broke it, he is exempt, for normally people do not look where they walk. If David was hurt, Levi is liable.

Rambam (6): If Levi left a jug in a place where he may do so, e.g. the corner of a winepress, and David stumbled on it and broke it, he is liable. If David was hurt, Levi is exempt, for David should have watched where he walks. If it was dark, or he filled the path with jugs, David is exempt for breaking them and Levi is liable if David was hurt. The same applies to all similar cases.

Poskim

Shulchan Aruch (CM 379:20): If a person fell in a pit and died, even if he was blind or fell at night, the owner is exempt. If he or an alert animal fell in, the owner pays full damage.

Gra (26): This opinion applies to 'animals should look where they walk' only regarding death. We learn from damages to man. We say that even seeing people do not look where they walk). Rava (24b) supports the other opinion (he taught that a walking cow has the right to walk over the crouching cow).

Rema: Some exempt even for damage to an alert animal if it fell during the day.

Shulchan Aruch (CM 412:1): If Levi left a jug in Reshus ha'Rabim, and David stumbled on it and broke it, he is exempt, for normally people do not look where they walk. If David was hurt, Levi is liable.

Shulchan Aruch (2): If Levi left a jug in a place where he may do so, e.g. an empty place in front of the olivepress, and David stumbled on it and broke it, he is liable. If David was hurt, Levi is exempt, for David should have watched where he walks. If it was dark, or he filled the path with jugs, David is exempt for breaking them and Levi is liable if David was hurt.

SMA (3): Even though the Shulchan Aruch says 'he filled the path with jugs', it was possible to go around or walk over them. Therefore, David is exempt only if he tripped. After this, the Shulchan Aruch discusses when it was impossible to pass. Then, David is exempt even for overtly breaking them.

Shulchan Aruch (ibid.): The same applies to all similar cases. If he filled the entire path with jugs and it is impossible to walk, David is exempt even for breaking them intentionally. However, if he was hurt by the shards while breaking them, Levi is exempt even if he filled the entire path, for David damaged himself.

Beis Yosef (DH u'Mah she'Chosav v'Im): The Halachah does not follow Shmuel, who says that people look where they walk when there is light. However, one must look in a place prone to be filled with jugs. We infer that if one put a jug where he may do so, if it is dark, people do not look, so it is as if he put it where he has no permission to do so.

Shulchan Aruch (3): Only man does not normally look where he walks. An animal's eyes are down; it normally looks where it walks. Therefore, if it tripped and was hurt by Levi's jug in Reshus ha'Rabim, Levi is exempt. If it broke it while walking, this is Regel, and it is exempt. If it kicked, this is Keren, and it is liable.