In general, we permit such untruths when they are defensive – when they protect against undeserved harm

At the end of our parsha, Yosef’s brothers send him a touching message from their late father:

When Yosef’s brothers saw that their father was dead, they said, “What if Yosef still bears a grudge against us and pays us back for all the wrong that we did him!” So they sent this message to Yosef, “Before his death your father left this instruction: So shall you say to Yosef, ‘Forgive, I urge you, the offense and guilt of your brothers who treated you so harshly.’” (Bereshis 50:15-17)

Chazal (Yevamot 65b, Yerushalmi, Pe’ah 1:1) tell us that the brothers bent the truth of this story for the sake of peace. The Gemara in Yevamos continues to explain that sometimes a fib is actually a mitzvah, giving the example of Shmuel: Hasehm instructed him to make up a cover story in order to fulfill the commandment to anoint Yishai’s son in Beit Lechem without incurring Shaul’s wrath. 

Moreover, sometimes even Hashem amends the truth, which Chazal note from the tale of Avraham and Sarah as they were told they would have a child. Sarah was surprised to hear she will give birth, exclaiming “My lord is aged!” When Hashem relays the story to Avraham, he quotes her as saying: “I have aged.”

Halachically, the cases of Shmuel and Avraham exemplify two quite distinct leniencies to alter the truth. In the case of Avraham, the sole intention is to prevent unnecessary wounded feelings. This leniency is halachically quite broad (though practically speaking, it is always worth considering if perhaps hurt feelings can be avoided some other way).

Shmuel, however, obtained direct benefit from misleading Shaul. Such an untruth is quite problematic. Normally, the prohibition of geneivas da’at (deception, or literally “theft of the mind”) forbids not only lying or misleading but even passive benefit from a misunderstanding. For example, if a non-Jew has a reasonable basis to assume that meat is kosher, the Jewish seller must pro-actively inform him if it is not kosher (treif). Even though non-Jews don’t insist on kosher meat but only prefer it, and even if the price is that of non-kosher meat, one must still clarify that the meat is not kosher (Chullin 94a-b).

In general, we permit such untruths when they are defensive – when they protect against undeserved harm. Shaul had no right to keep Shmuel from his prophetic mission, hence it was proper for him to make up a story that would enable him to fulfill it. Another example in the Gemara concerns a dishonest innkeeper who stole the purses of the Tannaim Rabbi Yehuda and Rabbi Yosi. Due to the circumstances, they were within their rights to trick the inkeeper’s wife into thinking he instructed her to return them (Yoma 83b).

The brothers’ fib to Yosef fits both leniencies. It is true that Yosef agreed to continue to provide for them, saying “fear not, I will sustain you and your dependents.” But the brothers did not request any benefit from Yosef or imply that Yaakov requested one. The request was merely for Shalom, for forbearance for their mistreatment of him twenty years prior.

The brothers could also rely on the second leniency of protection. Rashi tells us that Yaakov would never have suspected the righteous Yosef of avenging himself on his brothers, but the Torah tells us that the brothers themselves were apprehensive. Yosef could have used his authority to punish them arbitrarily; the Netziv suggests that the situation could even have been considered pikuach nefesh (danger to life).

The Netziv, differing from Rashi, explains that the brothers did not fabricate Yaakov’s request, but only interpreted it. Yaakov’s blessing to Yosef states: “Archers bitterly assailed him; they shot at him and harried him. Yet his bow stayed taut, and his arms were made firm” (Bereshis 49 23:24). The brothers interpreted this to mean that even though Yosef was assailed by his brothers, his arms were to remain firm, without reprisal. 

The Netziv’s interpretation teaches that even when social harmony and legitimate self interest can justify bending the truth, interpretation is always better than fabrication.