Midrash su Deuteronomio 27:5

8) R. Yochanan b. Zakkai said (Devarim 27:6) "Of whole (shleimoth) stones shall you build the altar of the L–rd your G d, etc.": "stones which make peace" (shalem). Now does this not follow a fortiori: If stones, which do not see, and which do not hear, and which do not speak — because they "make peace" between Israel and their Father in heaven, Scripture writes (Devarim 27:5) "You shall not lift iron over them," then a man who makes peace between a man and his wife, between family and family, between city and city, between country and country, and between one people and another — how much more so will calamity not befall him!

... “Moab is my washbasin…” (Tehillim 60:10) When Israel entered into their land in order to inherit it, the Holy One forbid them to conquer these three nations, as it says “Do not distress the Moabites…” (Devarim 2:9) So too regarding Edom it is written “You shall not provoke them…” (Devarim 2:5) From where do we learn that they were not to conquer the land of the Pelishtim? Because it is written “God did not lead them [by] way of the land of the Philistines for it was near…” (Shemot 12:17) The oath which Avraham swore to Avimelech was still near in time, “And now, swear to me here by God, that you will not lie to me or to my son or to my grandson…” (Bereshit 21:23) His grandson was still alive. In the future the Holy One will permit Israel to conquer all three, as it says “And they shall fly of one accord against the Philistines in the west, together they shall plunder the children of the East; upon Edom and Moab shall they stretch forth their hand, and the children of Ammon shall obey them.” (Yeshayahu 11:14) And it is translated as ‘they will join shoulder to shoulder as one to wipe out the Phillistines.’ Therefore it says “…Philistia, join me…” (Tehillim 60:10), Edom and Moav are their occupation as it says “Moab is my washbasin; on Edom I will throw my lock…” (ibid.)

R. Johanan the son of Zakkai said: Scripture states: Thou shalt build the altar of the Lord thy God of unhewn stones (Deut. 27:6), for it will help to achieve peace between the Israelites and their Father in heaven. A logical conclusion may be derived from this. If the stones of the altar, which cannot see or hear or speak, achieve peace between Israel and their Father in heaven, so that the Torah commands that iron should not be wielded over them, how much more so, then, should one who promotes peace between husband and wife, or between a man and his companion, have his days and his years prolonged.