EXOD505 We should try to make peace between people who are quarreling. Stones used for the alter in the Bais Hamikdosh (Holy Temple) were ruled unfit for use if they were touched by an iron implement (Rambam, Hilchos Bais Hamikdosh 1:15). Rashi cites the Mechilta which explains that because the altar established peace between Israel and their Father in heaven, it was forbidden to use an instrument of violence in its construction. The Mechilta proceeds with a kal vechomer (an inference from minor to major): "Stones do not see, hear or speak, but because they establish peace, the Torah said that you shall not lift up your sword upon it; therefore someone who makes peace between a man and his wife, between one family and another family, between a man and his fellow man, will surely merit that no harm shall befall him."