The Deen of Islaam is a Deen that comprises`Aqeedah (matters of Faith) and Sharee`ah (Laws, Legislation, and Judicial aspects). We indicated some of its Laws and mentioned its Arkaan which are considered the basis of its Legislation. As to the`Aqeedah Al-Islaamiyyah (The Islamic Creed), its basis are:
The Belief in Allaah, His Angels, His Books, His Messengers, the Last Day, and al-Qadar, its good and bad.
These bases are verified by evidences from the Book of Allaah (i.e. The Qur’aan) and from the Sunnah of Allaah’s Messenger sallallaahu `alayhi wa sallam. In His Book, Allaah says:
It is not al-Birr (piety, righteousness, and each and every act of obedience to Allaah, etc.) that you turn your faces towards east and (or) west (in prayers); but al-Birr is (the quality of) the one who believes in Allaah, the Last Day, the Angels, the Book, the Prophets. (Qur’aan 2:177).
He (ta `aalaa) says about al-Qadar:
Verily, We have created all things with Qadar, and Our Commandment is but one, as the twinkling of an eye. (Qur’aan 54:49-50).
In the Sunnah of Allaah’s Messenger, the Prophet sallallaahu `alayhi wa sallam said in his reply to Jibreel (Gabriel) when the latter asked him about Eemaan (Faith):
“Eemaan is to believe in Allaah, His angels, His Books, His Messengers, and the Last Day, and to believe in al-Qadar, its good and its bad.”
 Al-Qadar is the Ability of Allaah, where He Knew, Wrote, Willed and Created all things in predestined proportions and precise measures. See “The Salaf’s Understanding of al-Qadaa’ wal Qadar.” by Dr. Saleh As-Saleh, may Allaah have mercy on him.
 Collected by Imaam Muslim.