Why does the Torah write that the brothers saw that their father had died? Is it not obvious?
Rashi, from Bereishis Rabah 100:8: What the Torah means is that they saw signs that Yosef changed his attitude after Yaakov had died. They tended to regularly eat by him, and, as long as Yaakov was alive, Yosef would befriend them; but the moment he died, he kept his distance. The brothers feared that he hated them 1 and intended to avenge what they had done to him, which explains why they approached him with the request stated in the following Pesukim (50:16-17).
Riva citing a Midrash, Ba'al ha'Turim: After burying Yaakov, the brothers saw Yosef reciting a Berachah ('She'Asah Li Nes ba'Makom ha'Zeh'), which they misconstrued as his reliving the harm that they had done to him.
Malbim: In their father's lifetime, there was brotherhood between them due to their father, in whom all were partners - "ha'Lo Av Echad l'Chulanu" (Mal'achi 2:10). Until he was properly buried and eulogized, there was brotherhood because all were partners in the Aveilus and crying over one father. Also this arouses love. Now they realized that nothing unifies them. Brotherhood itself will arouse hatred, when he remembers what they did to him!
If so, why did Yosef do this? Refer to 50:15:1.1.
What does "Lu Yistemeinu Yosef" mean?
Rashi, Targum Onkelos and Targum Yonasan: It means 'Perhaps Yosef will hate us. 1
Hadar Zekenim, Ba'al ha'Turim #1: 'If only Yosef would hate us (only) in his heart (and not take action against us).'
Ba'al ha'Turim #2: May he return to us all the 'evil' that we did to him!' He became king of Egypt as a result of our having sold him - may he do so to us.
Rav C. Fogel: 'If only Yosef would hate us [and try to harm us]' - for when we tried to harm him, Hashem made him king!
Ohr ha'Chayim: The Torah says "Lu." They feared lest Yosef return their evil - the Torah says, if only he would do so, and they would be pained like they pained him! However, he did not; so other afflictions came due to their sin - Galus Mitzrayim, the final Galus, the 10 Harugei Malchus.
Malbim: "Im Ra'ev Sona'acha, Ha'achilehu Lachem" (Mishlei 25:21) - The greatest vengeance against one's enemy is if in place of the hatred and evil that he did to him, he puts him to eat at his table and does only good and Chesed to him. Then he constantly remembers the evil that he did! They said, he surely hates us - if only he would do to us evil, for the good that he does to us is like stabbing with a sword!
Ha'amek Davar: "Lu" here means 'if,' as in the Pesukim, "Lu Chachemu" (Devarim 32:29); "v'Lu Anochi Shokel Al Kapai" (Shmuel II 18:12). "Yistemeinu" is thought and investigation how to do evil, like I explained above (to 49:23). It would not be easy for Yosef to sell his brothers to be slaves, even if he is a great ruler, but "if he investigates, he will find a way to return to us [our evil]." They did not suspect that he would kill them. (The prefix Vav in "v'Hashev" is merely to beautify the expression, like "va'Yomer El Benosav v'Ayo" (Shemos 2:20); or to mean he will gradually use other [strategies] until he will achieve [returning the evil].)
'The word Lu' has connotations of 'if only,' or of a request (see Rashi for examples of each one). This is the only time that it means 'perhaps' (i.e. something that one does not want to occur). See also Sifsei Chachamim, and our other answers to this question.
QUESTIONS ON RASHI
Rashi writes: "'Yosef's brothers saw' - ... In the past, Yosef would draw them close, out of respect to his father; but when Yaakov died, he no longer drew them close." Can we say such a thing about Yosef ha'Tzadik? Why did Yosef do this?
Sifsei Chachamim (citing Midrash Raba): In fact, Yosef did so because until now, he had sat at the head of the table, because his father had placed him there. Now that his father was no longer alive, he felt that to do so would be a slight to Yehudah, who was king, and to Reuven, who was the Bechor. On the other hand, it would be degrading for him, in his position as viceroy of Egypt, to sit below them.
Gur Aryeh #1: Prior to Yaakov's death, Yosef was even closer to his brothers than is normal; they would eat at his table always. Now, Yosef no longer went that far.
Gur Aryeh #2: Yosef knew that after Yaakov's death, our subjugation to Egypt had begun (Rashi to 47:28). Yosef was afraid that if he, ruler of Egypt, was constantly found with his brothers, the Egyptians' "Havah Nischakemah Lo" (Shemos 1:10) would take the form of an outright war against them. 1 He had to show [as if] he had nothing to do with his brothers. 2
Rashi writes: "Some instances of the word 'Ulai' indicate a request..." Why is that relevant? We are discussing the word "Lu"!
Gur Aryeh: Rashi shows how every meaning of the word "Ulai" is also true of the word "Lu," such as 'if only,' and 'maybe.' It therefore follows that if "Ulai" can also mean 'but perhaps...,' then the word "Lu" can mean this as well.
