Telling a lie for the sake of peace:[1]

One may not tell a lie to his friend even for the sake of peace. Now, although the Sages[2] state that it is permitted [and even a Mitzvah[3]] to change the facts [i.e. lie] for the sake of peace, nevertheless, one may only lie for the sake of peace regarding a past event. However, he may not tell a lie regarding future matters. [Nevertheless, this matter needs further analysis, as an argument can be made that it is permitted to lie for the sake of peace even regarding a future matter.[4]]

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[1] Admur O.C. 156:2; M”A 156:1; Sefer Chassidim 426; Tosafos Bava Metzia 23b; Rambam Deios 5:7; Semag 107; Pela Hayoeitz “Hasheker”

[2] Yevamos 65b;

[3] Admur in parentheses; Rif in Bava Metzia Perek Eilu Metzios 23b

[4] Admur ibid in parentheses that this above ruling, “Requires slight analysis being that peace is greater than all the other mitzvah’s [see Midrash Raba Chukas 19:27 on verse Tehillim 34:15 “Bakesh Shalom Veradfeihu”; Vayikra Raba 9:9] and the Talmud [Yevamos 65b] permits one to lie for the sake of peace, and the Rif [Bava Metzia Perek Eilu Metzios 23b] even holds that it is a Mitzvah to do so, and hence from where can one conclude that one may not lie regarding future matters, as in truth perhaps it is permitted, as it states Bechol Derachacha Deieihu. [Brachos 63a even for an Aveira and Rashi there that sometimes one should even transgresses if it is for the need of a mitzvah; Midrash Raba Bereishis 1; Elya Raba 156:2; Peri Megadim 156 A”A 2]”