Nadab and Abihu
Rabbi Shimon says that in a way Nadab and Abihu died twice, once before God when offering the sacrifice, and once because they left no children, as someone who does not merit children is considered as though dead. We learn that Nadab and Abihu died physically but did not die spiritually because they were reincarnated in Pinchas. The reason they were reincarnated together in one body was because they had not married and so were only considered a half body each. Their sin was later corrected by Pinchas' action in slaying the foreign woman. The two sons of Aaron and Zimri had essentially committed the same sin, that is, bringing near something that was far from holiness. Rabbi Shimon talks about the covenant of peace. We learn that Rabbi Yosi had said that people have their sins forgiven when they feel compassion for afflictions visited upon the just; therefore during Yom Kippur people read about the death of the two sons of Aaron, and they feel distress for them so that their own sins are forgiven. Also, they are reassured that their own children will not die during their lifetimes.