祭祖为什么要用生羊来拜

羔羊 — — 無辜，純、 良性 — — 直古以來各宗教及各种族使用的象徵。
希臘,埃及,波斯等等

The Lambs of Gods

by R.R. on APRIL 10, 2012

     The lamb – innocent, pure, benign – has been a symbol used by various religions since early times. The lamb was the sin offering of ancient pagans. Greeks and Egyptians venerated the lam or ram, the ram’s horns often a centerpiece on the foreheads of their gods.

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http://chimeralinsight.com/the-lambs-of-gods/