Du'aa' has a very strong relationship with one's 'aqeedah (creed) [عقيدة, plural: 'aqaa'id ع...
By the third Hijri century, the specialists in the field of 'aqeedah (dogma, creed and faith) used the term "sunnah" to refer to the foundations of the faith, the well-established obligatory deeds, the matters of creed and the definitive rulings of Islaam...