NUM268 The Midrash (Otzar Hamidrshim, Midrash Hagadol Ugedolah, p. 78) says that without peace there is nothing as it is equated with everything in the world. Based on the verse in the Psalms (Psalms 34:15), another Midrash (Yayikrah Rabbah 9:9) states that peace is the only mitzvah one is commanded to actively run after to achieve. Other commandments are obligatory only if they happen to come your way--you must then observe them. But a person must actively seek peace, even if it is not easily achievable. Aaron the High Priest is described as one who actively "ran after peace" (Avot 1:12 and would actually lie to two fighting individuals (saying to each that the other one admitted his mistake and wants to make up) in order to bring them together (Avot DeRabbi Natan 12). And it was Aaron, the man of peace, who was the most beloved leader of Israel. When he died, it says [this verse] the entire congregation of Israel wept, but upon Moses' death, it merely says (Deuteronomy 34:8) that the people (but not all) cried (Avot deRabbi Natan 12).