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Ahlul Bayt Digital Islamic Library Project: The Last Will of Ali Ibn Abi Talib
Here is the will of Ali ibn Abi Talib, which he gave to his two sons, "after the attempt on his life by a stab from Ibn Muljam" in which he advises his sons "to be conscious of Allah" and follow the teachings of the Koran.
Islami City
Islami City: Islam History the Rightly Guided Caliphs
Good article on the first four caliphs of Islam. The reign of each is summarized briefly, emphasizing their most important attributes, actions, and contributions to the Islamic community.
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Uthman Ibn Affan
Biographical information on Uthman Ibn Affan, which includes facts about his personal life, his rule as Caliph of Muslim, and several quotes.
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Al islam.org: Sayings of Imam Ali Ibn Abi Talib
Here are the famous "sayings of Imam Ali," the fourth Caliph of Islam.