Spreading the science of Hadith and the principles of collecting and writing it
Given that the science of Hadith is one of the Shari`ah sciences and one of the obligatory sciences that should be learned, it is an obligatory duty to take care of it and show interest in setting rules and recording it. Therefore, Allah (Glory be to Him) guided those virtuous, trustworthy, and famous scholars who memorized its laws, were cautious when writing it to convey it from their ancestors downwards. They conveyed it exactly as they heard it, and Allah made this science beloved to them to protect His Religion and guard His Shari`ah. This science has been fresh and pure since the time of the Messenger (peace be upon him), and the religion is still strong and coherent till now. It is still the noblest science in the sight of the Companions, the Followers, and those who followed them. The greatest honor of which they boasted after the memorization of the book of Allah was the knowledge of Hadith science, so desires were strong and determinations were high to learn it. Some of them used to travel for a long distance across deserts to listen to one Hadith. Some would desire to learn the Hadith, whereas others wanted to listen to the Hadith from its original narrator for his trustworthiness, truthfulness, or for seeking the high chain of narration, so people were competing to learn it.
First, their dependence was on memorization without paying attention to what they wrote down exactly as they memorized the Book of Allah (may He be Glorified and Exalted). However, when Islam spread; the Muslim state expanded; the Companions of the Prophet spread in countries; many countries were opened for Islam; most Companions died and their friends and followers scattered; and accuracy decreased; scholars needed to write down Hadith; by Allah, writing down Hadith is the origin because minds forget and memory may become deficient, but the pen writes down without forgetting.
So, the matter ended up to a group of scholars such as `Abdul-Malik ibn Jarij, Malik ibn Anas, and others in their time who wrote down the Hadith.
It was said that the first book was wrote in Islam was the book of Ibn Jarij, while others said: Muwatta' Malik may Allah be merciful with them.
Others said: The first one wrote and classified Hadiths was Ar-Rabi` ibn Sabih in Basra.
Then collecting and writing the Hadith spread and books and chapters were written until the time of the great two imams: Abu `Abdullah Muhammad ibn Isma`il Al Bukhari and Abu Al Husayn Muslim ibn Al Hajjaj An-Naysabury (may Allah bestow mercy upon them) who wrote their books. May Allah reward them for the efforts they saved for Muslims and for taking care of the religious matters as they recorded only authentic Hadiths in their books.
Later on, we shall mention the conditions on which they depended in writing their books as well as the valid and invalid Hadiths in details with Allah's Willing. They were the first to call their books Sahih "authentic Hadiths". They were sincere in their writing down their books, therefore Allah granted them good acceptance in the east and the west, acceptance to their sayings, and spread of their book which is apparent and does not need a proof; all these were because of their truthful and good intention as well as the authentic Hadiths which they recorded in their books.
Then this kind of classification, collecting, and writing spread in Muslim countries, then the purposes of people scattered and their objectives diversified until it was the time of a group of scholars who collected and wrote in this science such as Abu `Eisa Muhammad ibn `Eisa At-Tirmidhy, Abu Dawud Sulayman ibn Al Ash`ath As-Sijistany, and Abu `Abdur-Rahman Ahmad ibn Shu`ayb An-Nasa'y (may Allah show mercy to them all) among other countless scholars. That time was like the essence of all times in collecting this science, as it seemed to be the peak of this science.
Later on, seeking this science decreased, interests abated, and determinations became low. This is the law of every science, it grows bit by bit until it reaches its peak then it goes downwards. So, it seems that the peak of the knowledge was in the time of Al Bukhari and Muslim and the scholars of their time then it has decreased until our time; this is the way of Allah in His Creation, and there is no way to change that.