The Deen of Islaam, as it is discussed above, is a Deen that compromises ‘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 Islaamic Creed), its basis is:
The Belief in Allaah, His Angels, His Books, His Messengers, the Last Day, and Al-Qadar , its good and bad.
These basis are verified by evidences from the Book of Allaah (i.e. The Qur’aan) and from the Sunnah of Allaah’s Messenger (sal-Allaahu ‘alayhe 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 (sal-Allaahu ‘alayhe 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 book “Al-Qadaa’ wal Qadar” by this translator.
 Collected by Imaam Muslim.