Iman e Mufassal (The details of Faith) is that a Muslim should know those matters related to Ar-Rububiyyah (i.e. believing that Allah is the only Creator, Cherisher, Sustainer), Al-Uluhiyyah (i.e. it is Allah Alone Who is worthy of true worship) and Al-Asmaa’ wa as-Sifaat (i.e. to correctly believe in all the Names and Attributes that Allah has described Himself with) and the evidence of each one of them and the understanding of other pillars of Iman (Angels, Books, Messengers/Prophets, Resurrection/Judgement and Decree).
Iman e Mujammil (The summary of Faith) is that a Muslim believes in the six pillars of Faith in general terms. For instance, he should believe in Allah as his Lord Who runs the affairs of His slaves as One God and he should not associate anyone as a partner in worshiping Him. He should also believe that Allah has the Beautiful Names and Attributes having the utmost degree of Majesty and Perfection and knowledge of other pillars of Iman.
In other words, Iman e Mufassal is to believe in the details of what the Prophets conveyed and Iman e Mujammil is to believe in all what they conveyed in general.
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﴾بسم الله الرحمن الرحيم﴿ 