One of the three things which Moshe Rabbeinu did on his own initiative and was later vindicated by Divine approval was separating from his wife after the giving of the Torah at Mount Sinai. His reasoning was that if all Jews were commanded to separate from their wives in the few days leading up to the Torah-giving in order to be properly pure for their momentary encounter with Hashem, then his separation must be an ongoing one since he was constantly being summoned to unscheduled encounters with Hashem.
Tosefot points out that the gemara's proof that this was Moshe's initiative rather than a Divine command is the fact that Aharon and Miriam became angry with their brother when they learned of the separation, and spoke critically of his action. (Bamidbar 12:1-2) Had Moshe been commanded in this separation, they would certainly not have questioned his behavior.
But if the same Aharon and Miriam were aware of Moshe's separation, then they were also aware that when Hashem gave permission to all the Jews to resume family life after the Torah-giving that He expressed His approval of Moshe's initiative to make a prolonged separation by stating "But you remain here with Me" (Devarim 5:27-28). Why then, asks Tosefot, were they upset by his initiative if it received Divine approval?
The answer, proposes Tosefot, lies in the Talmudic statement (Mesechta Makkot 10b) that Heaven guides a person along the path that he has chosen to follow. The catalyst for Divine sanction of Moshe's prolonged separation from his wife was his choice of a level of purity which his sister criticized as being beyond the norm expected of all Jews and at the expense of his wife. The Divine reaction to this criticism initiated by Miriam was the illness described in the above cited Torah chapter, which was to serve as a lesson to all future generations for guarding the tongue.
Right after the death of their father Yaakov, Yosef's brothers sent a message to Yosef that before his passing, Yaakov had asked them to implore Yosef in his name to forgive them for the evil they had done him. Yaakov, of course, had never made such a request, and from this, Rabbi Elazar the son of Shimon concludes that one may divert from the truth in order to maintain peaceful relations.
But indeed, why did Yaakov not anticipate the resentment Yosef might feel towards his brother and make such a request of him during his lifetime?
Ramban (Bereishet 45:27) contends that Yaakov never became aware that Yosef had been sold into captivity by his brothers. Yaakov always assumed that Yosef had been picked up by slave dealers while wandering in the fields and sold by them to the Egyptians. The brothers never told him because of their fear that he might become outraged and curse them as he did Reuven, Shimon and Levi for their sins in other matters. Yosef, for his part, was too moral to divulge such a matter to his father.
Rashi, in his commentary on Chumash, takes a different approach. Yaakov was aware, but he did not suspect his righteous son Yosef of harboring feelings of resentment which might lead to a vendetta, and therefore saw no need for asking him to forgive them. The question arises, however, as to why the brothers did suspect him and found it necessary to tell their "white lie?"
Maharsha suggests that the suspicion arose only after the death of Yaakov, so there was no need for them to seek their father's intervention while he was alive. The Midrash (Rabbah 100:8) mentions two things that happened which aroused their suspicion because they misconstrued Yosef's intentions. One was the fact that Yosef stopped inviting them to dine with him because he did not wish to continue the seating arrangement instituted by their father which placed him ahead of Yehuda the king, who was the forefather of the kings of the Jewish Nation, and ahead of Reuven the firstborn. Yet he was also unable to place them ahead of him because of his royal status in Egypt, and therefore decided to stop inviting them altogether. Another incident occurred when Yosef returned from his father's funeral and looked into the pit where his brothers had placed him. Yosef did this in order to offer a blessing of thanks to Heaven for his miraculous rescue from death. Although his motives in both cases were praiseworthy, they aroused his brothers' suspicions that animosity suppressed in their father's lifetime had now surfaced, forcing them to lie in order to keep the peace.