What exactly, was Yehudah's reason for changing the original plan, and selling Yosef to the Yishma'elim?
Seforno: Not only would they gain nothing by killing Yosef, but they would lose, inasmuch as their consciences would give them no rest. Moreover, killing him would not even serve as a warning for those who would harm them, since they would be obligated to keep his death secret 3 to prevent their father from finding out. Selling him to the Yishma'elim as a slave, on the other hand, would serve as a fitting punishment for his having intended to rule over them
Ramban: Reuven taught the brothers that it was better to throw Yosef into the pit and let him die (thereby causing his death) that to kill him with their hands. Yehudah now added that causing his death too, would be akin to murder. 4 Therefore it is preferable to sell him.
Hadar Zekenim: Since we cannot kill him openly, it is not revenge.
Malbim: People murder either to take the victim's money, or for revenge, to instill fear on others [to do like the victim did]. We will not get any money from Yosef, and we will need to cover his blood, so this will not put fear on people!
Hadar Zekenim - "v'Chisinu es Damo" - if we sell him, his Damim (value) will go in our Kis (pocket). Rosh - right after, it does not say 'rather, let us sell...', rather, "let us sell." This implies that also "v'Chisinu es Damo" refers to selling.
Over and above the fact that Yosef was their brother, and it would be wrong to sentence him to death. Refer to 37:26:1:3.
This is also how Rashi and Targum Onkelos interpret "and we will cover his blood". Whereas the Ramban explains it literally, anyone who commits a murder that he wants to hide, buries the body and covers the blood, as we find in Shemos, 2:12).
What is the meaning of "Mah Betza"?
Rashi (from Targum Onkelos): What monetary gain?
Ibn Ezra: What benefit?
Ha'Emek Davar: What compromise [is Reuven's idea not to overtly kill him? Also through Gerama, we kill him!]
Mei ha'Shilu'ach (cited in Daf Al ha'Daf Sanhedrin 6b): In any case, Yakov will not give to us Yosef's robe, it was for him.
It says in Sanhedrin (6b) that whoever is Mevarech (blesses) Yehudah for saying "Mah Betza", he blasphemes. What is the reason?
Rashi (6b): Since his brothers heeded him, he should have said to return him to Yakov.
Chizkuni: Yehudah implied that if there were benefit through killing him, we should kill him. Maharsha (6b) - i.e. he should have said, we cannot kill him due to Yir'as Shamayim!
Maharsha (6b): 'Mevarech' means 'curses', as in Melachim (1:21:17). Yehudah intended l'Shem Shamayim. He feared to suggest that they return Yosef to their father, lest the brothers not heed him. Yehudah's name is based on Hashem, so one who curses him, he blasphemes. 1
Mei ha'Shilu'ach (cited in Daf Al ha'Daf Sanhedrin 6b): Yehudah gave a logical reason (refer to 37:26:152:4) in place of the Halachah (it is forbidden to kill)! One may do so at a time of temptation. One who does so at other times, he blasphemes. One must serve Hashem without other reasons and intents!
Kedushas Levi (Chidushei Agados, citing his son R. Meir): One who praises Yehudah for not killing Yosef, he equates Yehudah to simple, lowly people. This is not a praise for a great person like Yehudah!
Harchev Davar (based on Tanchuma): After the brothers ate and were about to bless, Yehudah said 2 'we want to kill a soul, and we bless Elokeinu?! This is blasphemy!'
See Torah Temimah, note 21. Oznayim la'Torah: And it is because of the good deed that Yehudah performed that the Torah mentions his name, as opposed to Shimon and Levi in Pasuk 19, whose names the Torah does not publicize. Refer also to 37:22:4:1.
I.e. the Gemara means that Yehudah said that also this 'compromise' to merely cause his death,to bless Hashem amidst this, is blasphemy. (PF)