Definition of Sunnah according to scholars of Hadith, Usul-ul-Fiqh, and Fuqaha' and the difference between them

Q: How obligatory is it for a Muslim to abide by the Sunnah? As an Egyptian, I hear from the scholars here in Egypt that the Sunnah in general includes the sayings and actions of the Messenger of Allah (peace be upon him). If I perform them, I shall gain reward from Allah; if I do not, I shall not be deprived of the reward nor be committing a sin. That is why I am writing to you, as I find great discrepancy between what I have learnt in Egypt and the books and articles I read here in Makkah written by many scholars.Secondly, please give me the titles of some books which deal with this issue so that I can buy them. Please enlighten me, may Allah enlighten you.

A: First, according to the Hadith scholars, the Sunnah refers to everything that was authentically reported from the Prophet (peace be upon him), whether they are sayings, actions, approvals or moral and physical attributes. (Part No. 4; Page No. 359) According to the scholars of Usul-ul-Fiqh (principles of Islamic jurisprudence), they clarify the difference between Sunnah and the other sources: the Qur’an, Ijma‘ (consensus), Qiyas (analogy) and Athar (narrations from the Companions). According to Fuqaha’ (Muslim jurists), the Sunnah refers to whatever is commended by Shari‘ah without an obligation to do it; those who do it are rewarded, while those who do not are not punished, such as Salat-ul-Duha (supererogatory Prayer after sunrise), offering two or four Rak‘ahs (units of Prayer) before the Zhuhr (Noon) Prayer, Sawm (fasting) on the Day of ‘Ashura‘ (10th of Muharram) and on three days every month, and so on. In this sense, Sunnah is a degree between a Fard (obligation) and a Mubah (permissible). It is also used to refer to the linguistic meaning of the word, which is "the way". This is its general meaning and there is no contradiction between its other meanings; rather the difference between them arises from the diversity of the branches of sciences studying Sunnah and the terms used by the scholars in each branch. Second, you can refer to the definition of the Qur’an, Sunnah, Hadith and Athar in the books on the sciences of Hadith and Usul-ul-Fiqh, in addition to the chapters on optional Salah and Sawm and similar books of Fiqh (Islamic jurisprudence).May Allah grant us success. May peace and blessings be upon our Prophet Muhammad, his family, and Companions.