The imitation of the later to the former and the reason for abridging and writing their books
When those figures were the pioneers in that science, their work was imperfect because their main goal was to protect Hadiths by writing them down, warding off lies, filtering fabricated Hadiths, examining their chains of narration and the memorization of narrators, their trustworthiness, and their conditions to the extent that they filtered them, criticized narrators, praised others, took Hadiths from some and left others. That was done after taking precautionary measures, careful examination, and taking the necessary procedures, so that was their main goal and purpose but time was not enough to take further steps. Furthermore, they never thought of engaging in other works, but it was not permissible for them to do so because first they had to prove the authenticity of Hadiths then arrange conditions of narrators, this is the origin, then to arrange and improve its status. They did what they had to do and died without completing their work after they had paved the way for successors and those who followed them and troubled themselves for the comfort of those who will come after them. Then it was the time of the Righteous Successors who wanted to spread this great virtue and this science for which scholars had finished their lives to collect and detail its benefits through a creative arrangement, good classification, abridging and simplifying, deducting rulings, and explaining odd words.
Among those later scholars some gathered the books of the former with slight abbreviation as Abu Bakr Ahmad ibn Muhammad Al Barqany, Abu Mas`ud Ibrahim ibn Muhammad ibn `Ubayd Ad-Dimashqy, and Abu `Abdullah Muhammad ibn Abu Nasr Al Humaydy did. They collected the books of Al Bukhari and Muslim and arranged their books according to narrators not chapters as was previously mentioned.
Later on, Abu Al Hasan Razin ibn Mu`awiyah Al `Abdary As-Saraqusty followed them in collecting the books of Al Bukhari, Muslim, Al Muwatta', the compilation of Abu `Eisa At-Tirmidhy, Sunan Abu Dawud As-Sijistany, and Sunan Abu `Abdur-Rahman An-Nasa'y (may Allah bestow mercy on their souls). He arranged his book according to topics not according to the chains of transmission without explanations or Tafsir and perfected their work for those who will come after them; may Allah reward them all.