Mitzvah D'Ohraysa:

It is stated in Sefer Charedim (2:57): "To seek peace and pursue it is a d'ohraysa, as even in times of war one must seek peace, as is stated (Devarim 20:10): 'When you come close to a city to fight a war and you shall call to it with peace.' And the Semag counts it as a mitzvas asei"

He continues: “Wherever there is peace, the satan cannot harm us, as is stated (Hoshea 4:17): 'Efraim is joined to idols; let him alone.' And Hashem ordered that His holy name that is written in sanctity should be erased in water (in the case of a sotah) in order to make peace between a husband and wife. One who wants to merit this mitzvah (of pursuing peace) should also be careful to always judge others favorably."