Good friday commemorates the cruxification of Jesus Christ but also reminds the beginning of spring, Pesach, in jewish Calendar, the Passover, the Feast of Unleavened Bread. It is also called Chag HaMatzot (the Festival of Matzah). It commemorates the Exodus and freedom of the Israelites from ancient Egypt.
On a meta-level, the cruxification and the exodus are strongly related to each other.
The lamb is a symbol for both events.
