What does it mean by, "except for the bread that he ate"?
Rashi (from Sanhedrin 75a), Targum Yonasan: It is referring to his wife 1 - only the Torah uses a more refined way of saying it. 2
Rashbam: It means literally the food that Potifar ate. He saw it on the table after Yosef purchased and prepared it.
Rosh, Moshav Zekenim, Da'as Zekenim, Ramban #1 (citing the Ibn Ezra): It is his food, which Yosef was not even allowed to touch. 3
Ramban #2: Potifar was unaware of Yosef ever taking anything of his for himself, other than the food that he ate. 4
Ha'amek Davar, citing his son: Yosef ate only Potifar's bread, which was Kosher, but not his meat and wine - and even so, "he was Yefeh So'ar vi'Yefeh Mar'eh"!
See Ba'al ha'Turim. Sifsei Chachamim - We must say so, for Yosef said (in 39:9) that Potifar withheld from him only his wife! Da'as Zekenim rejects the proof. Yosef did not bother to mention the bread.
Rosh, Hadar Zekenim: And we find that eating is a euphemism for intimacy - 'Achlah u'Machasah Fiha" (Mishlei 30:20).
Since the Egyptians considered eating together with the Ivrim an abomination (See 43:32).
See Ramban.
Why does the Torah insert, "va'Yehi Yosef Yefeh So'ar vi'Yefeh Mar'eh" here?
Rashi: This connects with the following Parshah. The moment Yosef saw that he was in charge, he began to eat and drink [nicely], and to curl his hair. Ha'Kadosh-Baruch-Hu said, 'Your father is mourning for you, and you are curling your hair?! 1 I will incite the bear against you!' - Immediately, "The wife of Yosef's master set her eyes on him" (39:7). 2
Ramban and Seforno: This connects with the following Parshah. It was because of Yosef's good looks that his master's wife set her eyes on him.
It connects to the previous words. Refer to 39:6:1:5.
Ha'amek Davar: Normally, hard work ruins one's appearance. Even though Yosef had many affairs, he did not toil so much due to Divine success.
Harchev Davar: Learning saps one's strength (Sanhedrin 26b) and beauty. Bereishis Rabah (86:5) learns from "Nashani Elokim" (41:51) that at the end, Yosef forgot the Torah. Because he did not toil enough in Torah, he kept his beauty, and Potifar's wife accosted him. 3
Gur Aryeh: Why interpret this way? It doesn't matter why Potifar's wife set her eyes upon Yosef, be he beautiful or not! So why mention his appearance here? It must mean that it was because of Yosef's improper conduct, i.e. that he indulged in self-beautification while his father mourned, that Hashem incited "the bear" against him.
Rashi: Hence, the next Pasuk says "Achar" (39:7), which means immediately afterwards, as opposed to 'Acharei,' which means much later. Refer to 15:1:1:1; and refer to 40:1:151.
This is difficult. R. Yishmael Kohen Gadol and R. Yochanan were exceedingly beautiful; R. Yochanan said that it would be Chilul Hashem if he went four Amos without Torah (Yoma 86a)! The Midrash says that at the end, Yosef forgot, i.e. but not now! And in any case, we need not say that it was due to Bitul Torah. Why would Yosef merit such great success amidst Bitul Torah?! Surely Harchev Davar means that Hashem was very exacting with him for a small Bitul Torah. (PF)
What does the Torah mean when it writes that Potifar abandoned everything in Yosef's jurisdiction?
Malbim: Initially, he checked on Yosef. Now he left everything to him [and did not think about it at all].
QUESTIONS ON RASHI
Rashi writes: "'Except for the bread that he would eat' - meaning his wife" (over whom Potifar kept watch, that she be intimate only with him). But Rashi writes (to 41:45) that Potifar had become impotent (for he had [initially] bought Yosef for purposes of sodomy)?
Gur Aryeh: Potifar was not made completely impotent; but rather just enough that he no longer had excessive desire for relations. Chazal (Sotah 13b) derive this, not from the term Saris in our Perek (39:1), but from the extra Ayin in the name Potifera in verse 41:45.
Rashi writes: "'Except for the bread that he would eat' - I.e. his wife; only that the verse uses a euphemism." Why is eating of bread a euphemism for marital relations?
Maharal (Nesivos Olam, Nesiv ha'Avodah Ch. 16, p. 126): Just as eating is being Mekabel food (taking in, incorporating); so too through their marital bond (Chibur), the husband and wife each 1 receive from the other.
Maharal: Our verse uses the term eating from the man's perspective, also see Mishlei5:15 (see Metzudos). Eating is also used as a euphemism from the woman's perspective (Mishlei 30:20). Also see Kesuvos 65b.
