The narrators of Hadeeth are the most honourable and respectable Muslims, as they are keepers and preservers of Sunnah. Most of them are the companions of the Prophet who witnessed the acts and learnt the sayings of the Prophet . Others are the successors of the companions. Who were blessed by Allah and they are highly respected by all Muslims. They are shinning stars of Islam.
Their hearts were free from worldly desires. Reading their biographies will increase love and devotion towards them and develop more interest to be faithful and obedient in the heart of the Muslim who reads their biography.
Allah Almighty Says (what means): "Verily, We have sent down the Reminder, and surely, We will guard it (from corruption)." [Quran; 15:9] The above promise made by Allah is obviously fulfilled in the undisputed purity of the Quranic text throughout the fourteen centuries since its revelation.
However, what is often forgotten by many Muslims is that the above divine promise also includes, by necessity, the Sunnah of the Prophet Muhammad for it is the practical example of the implementation of the Quranic guidance, the Wisdom taught to the Prophet along with the Scripture, and neither the Quran nor the Sunnah can be understood correctly without recourse to the other.
Allah preserved the Sunnah by enabling the Companions, may Allah be pleased with them, and their followers, may Allah have mercy on them, to memorize, write down and pass on the statements of the Messenger of Allah and the descriptions of his way, as well as to continue the blessings of practicing the Sunnah. Later, as the purity of the knowledge of the Sunnah became threatened, Allah caused the Muslim nation to produce outstanding individuals of incredible memory-skills and analytical expertise, who journeyed tirelessly to collect hundreds of thousands of narrations and distinguish the true words of precious wisdom of their Messenger from those corrupted by weak memories, from forgeries by unscrupulous liars, and from the statements of the enormous number of scholars, the Companions and those who followed their way, who had taught in various centers of learning and helped to transmit the legacy of Muhammad - all of this achieved through precise attention to the words narrated and detailed familiarity with the biographies of the thousands of reporters of Hadeeth. Action being the best way to preserve teachings, the scholars of Islam also revived the practice of the blessed authentic Sunnah.
Unfortunately, however, statements will continue to be attributed to the Prophet although the person quoting them may have no idea what the people of knowledge in the field of Hadeeth science have ruled regarding those hadeeths, thus ironically being in danger of contravening the Prophet's widely-narrated stern warnings about attributing incorrect/unsound statements to him.
The methodology of the expert scholars of Hadeeth in assessing narrations and sorting out the genuine from the mistaken, fabricated etc., forms the subject-matter of a wealth of material left to us by the scholars of Hadeeth (traditionists).
A Hadeeth is composed of two parts: the Matn (text) and the Isnaad (chain of reporters). A text may seem to be logical and reasonable but it needs an authentic Isnaad with reliable reporters to be acceptable. 'Abdullaah Ibn Al-Mubaarak (d. 181 AH), one of the illustrious teachers of Imaam Al-Bukhari said: "The Isnaad is part of the religion, had it not been for the Isnaad, then people would have claimed whatever they wished."
Among the sciences of Hadeeth is the study of the chain of reporters (the Isnaad). Many Muslim scholars have specialized in this field. It includes identifying the name of each and every narrator (reporter), his character (his truthfulness, piety, public behavior), his ability and reputation as a memorizer and the types of narrations he is known to report, whether authentic, weak, fabricated, etc. In addition, each narrator should be identified by a rating given by other narrators who knew him. So all of these and many other details must be considered to know the degree to which a Hadeeth may be used as a basis for Islamic belief or practice (Sharee’ah), or merely as a point of interest (not to be attributed to the sayings, etc. of the Prophet ).
After the Book of Allah (The Quran), the books of Hadeeth collection that were collected by Imaams Bukhari and Muslim are considered by the Muslim scholars to be the most authentic books of Hadeeth. However, there are other famous scholars in the field who compiled books of Hadeeth such as; Abu Daawood (d.275), At-Tirmithi (d. 279), An-Nasaa’i (d. 303) and others .