After Yaakov’s death, Yosef’s brothers are afraid he will now take revenge on them for selling him into slavery. They tell him that Yaakov himself ordered him to forgive them (Bereshit 50:15-17). The Gemara justifies this story, using it as an example of the principle “A person is allowed to change [the facts] for the sake of peace” (Yoma 65b).
Another well-known example of this idea is the custom to praise the bride with the expression “Kala naah vechasuda” – lovely and gracious bride”. Beit Shammai opposed using this phrase if the bride is lame or blind, pointing out that the Torah commands us “Distance yourself from lies” (Shemot 23:7). Not only is lying forbidden, but we are actually required to distance ourselves from it, avoiding even stretching the truth. Beit Hillel point out that the groom at any rate views the bride as lovely and gracious, and a person should adopt a point of view which takes account of other people’s views. We rule like Beit Hillel. (Ketubot 17a, SA EHE 65a.
Presumably Beit Hillel view the verse in Shemot as referring only to court judgment.)
The Midrash relates how Aharon would reconcile feuds by telling each side, “Your friend is not avoiding you because he bears you a grudge; on the contrary, he knows he is wrong and he is ashamed to face you.” By saying this to each side he was able to persuade both to forgive and forget (Avot DeRebbe Natan chapter 12).
We see that despite the supreme importance of truth, which is “the seal of the Holy One, blessed be He” (Shabbat 55a), peace (shalom) can be even more important. Yet this order of importance is valid only in exceptional circumstances. We learn this from the story of Rav and his son Chiya. Rav had a somewhat strained relationship with his wife, and in some areas she would do the opposite of what he requested. When Rav relayed directions through his son, he noticed that she would do what he requested. When he mentioned to Chiya that his mother seemed to be more cooperative, Chiya explained that this was only because he was reversing Rav’s directions!
Even though this is an obvious example of dissembling for the sake of truth, Rav asked his son to stop, citing a verse from Yirmiyahu (9:4) which accuses the wicked of accustoming themselves to lie. (A similar message seems to stem from the story of Kushta on Sanhedrin 97a.)
One way of understanding Rav’s direction is that peace is more important that truth once in a while, but not on an ongoing basis. A more consistent understanding is that peace is always the supreme value. Why then may not we lie to achieve peace on a regular basis? The answer is that the trade-off is a false one, because peace itself is dependent on truth. On an ongoing basis, being truthful is the surest way of creating harmony and trust, and being deceitful the surest way to create friction and enmity.
Only if we adopt a steadfast habit of being truthful and straightforward can a rare and occasional artifice be effective in fostering peace. The Midrash we mentioned about Aharon cites the verse, “A Torah of truth was in his mouth, and injustice was never found on his lips; with peace and righteousness he went with Me, and many he turned from sin” (Malakhi 2:6). Aharon’s peace stemmed from a basis of truth and righteousness.