In the Biblical account of Exodus, the Hebrews were instructed to mark the doorposts of their homes with blood from a lamb. During the tenth plague on Egypt, which was the slaying of their firstborn, the spirit of the Lord passed over the homes of the Israelites who had done as God instructed.
Recommended Resources
Offers a how-to guide along with stories, the history, recipes, multimedia and information about the Seder.
http://www.chabad.org/holidays/passover/default_cdo/jewish/Passover.htm
Details Seder symbolism and traditions. Offers videos about the history of Passover, the prophecies of Moses and Passover matzo. Also features an "Ask a Rabbi" section.
http://www.history.com/content/passover
Features the Seder, questions and answers, recipes, greeting cards and perspectives about Passover.
http://www.torah.org/learning/yomtov/pesach/
