The Science of the foundation of the Deen
The science of tawheed is the noblest of the sciences, and the foundation of the shari`a. Belief in Allah, His unification and knowledge is the causative factor behind Allah ta`ala revealing the Heavenly Books, and the sending of the Messengers. By means of the unification of Allah and knowledge of Him, a person may enter Paradise which is the desired goal of those who are blessed; as he, upon him be blessings and peace said: “Whoever dies bearing witness to that there is no deity except Allah, will enter Paradise.” It is for this reason Abd’r-Rahman ibn Muhammad al-Akhdari said in his Mukhtasar: “The first that is obligatory upon the responsible person is the rectification of one’s Imaan.” The spiritual master Ibn `Aashir in his al-Murshid ‘l-Mu`in said:
“The first obligation upon those who are responsible * Firm in the view is that they know
Allah and His Messengers by means of the attributes * From what has been established in verses.”
The erudite scholar of the Blacklands, Shaykh Abdullahi ibn Fuduye` said in his Manan’l-Manaan:
“And the most superior of the sciences is the foundation of the religion * And its superiority will be manifested until the Day of Judgment.”
It is for this reason this science is called Usuul ‘d-Deen (the Foundation of the Religion). The Shehu, may Allah be merciful to him said in his `Umdat’l-`Ulama: “Realize and may Allah give and you success that the religion with which our Prophet Muhammad, may Allah bless him and grant him peace came has its foundation and its branch. As for as its foundation, it is Imaan and the knowledge which corroborates Imaan is the science of Usuul ‘l-Deen (the Foundations of the Religion).” Then there branches from this foundation two branches.  An outward branch which is Islaam and the corroborating knowledge for it is the science of the shari`a and jurisprudence.  An inward branch which is Ihsaan and the corroborating knwliedge for it is the science of the Divine Reality and spiritual purification. Thus, Islaam and Ihsaan cannot be valid except with the verification of Imaan. It is for this reason the scholars agree that the first of the obligations upon every responsible person is to rectify one’s Imaan.
The Shehu, may Allah be merciful to him also said in his Mi`raaj’l-`Awaam regarding the meaning of phrase ‘the foundation of the religion’: “…which is the science of tawheed and it is divided into thre e divisions:  The first division is divinity (ilaahiyaat) which revolves around what is obligatory with regard to Allah ta`ala, what is impossible to Him and what is permissible with regard to Him.  The second division is prophetic (nabawiyaat) which revolves around what is obligatory with reagrd the messenges, uopon them be peace, what is impossible with regard to them and what is permisible with regard to them. And  third of division is the after-life (sami`aat) which revolves around what the Messengers upon them be blessings and peace informed us about regarding the matters of the Unseen.”
He also said, may Allah be merciful to him in his Fat’h al-Basaa’ir: “The discipline of tawheed is divided into two divisions:  usuul ‘d-deen (the foundation of the religion) and  `ilm’l-kalaam (scholastic theology). The science of the foundation of the religion is among t he sciences which are an individual obligation (furuud al-`ayaan), while the science of scholastic theology (`ilm’l-kalaam) is among the sciences which are collective obligations (furuud al-kifaaya).” It is from this that we realize that the science of the foundation of the religion is from amongte most important of the sciences which should preoccupy the beginners.
It is for this reason that the Shehu, may Allah be merciful to him composed this blessed concise and easy text which he called USUUL’D-DEEN. My spiritual master, Shaykh Muhammad al-Amin ibn Adam al-Khateeb said that the Shehu composed this book in the beginning of his affair, when he found the majority of the people ignorant of the science of the foundation of the religion. He thus composed the book USUUL’D-DEEN in order to firmly establish the common Muslims upon what will suffice them in this discipline. Th us, the text is a fundamantal book regarding the doctrine of the beliefs of the common people, but usually utilized to teach children.
Shaykh Muhammad Shareef bin Farid
Chongqing, Chongqing, the People’s Republic of China