Al-Ramhurmuzi (Persian: Ramhormozi 265-290 hijri), the Imam, the skilled Hafidh, the Muhaddith of the Persians, Abu Ahmad, Al-Hassan Ibn Abdul-Rahman Ibn Khalal Al-Farsi Al-Ramhurmuzi Al-Qadhi (the Judge), composer of the book ” المحدث الفاصل بين الراوي والواعي ” (Al-Muhaddith Al-Fasil bayn Al-Rawi wa Al-Wa’i) in the science of Hadith.
It is said that Al-Rumhurmuzi was the FIRST PERSON ever who had categorised the science of Hadith system (terms etc.). Although (according to some) it is more correct to say that it was Imam Al-Tirmidhi (from Persia/Khorasan city of Termez). A contemp. scholar of today named Shaykh Abdallah Al-Sa’ad says that if we were precisely then Imam Al-Shafi’i (in his book “Al-Risalah”) already set some basics for the science of Hadith (as have others like Ibn Hibban etc.), yet Imam Al-Ramhurmuzi basically set a complete scheme hence he is normally referred to the fist person ever who had categorised the different science of Hadith. This is acknowledged by one of the Kings of Hadith science Imam Al-Hafidh bin Hajr who said:
ذكر الحافظ ابن حجر ـ رحمه الله ـ في النخبة أن أوّل مَنْ صنّف في هذا العلم هو : أبو محمد الرَّامهرمزي (الحسن بن عبد الرحمن بن خلاد المتوفى نحو  هـ) ..صاحب (المحدث الفاصل بين الراوي والواعي)
Al-Hafidh bin Hajr – may Allah have mercy upon him – mentions in “Al-Nakhbah” that the first person who had classified this science [of Hadith] was Abu Mohammad Al-Ramhurmuzi (passed away in Hirji 360 […].
Therefore Al-Ramhurmuzi stands out because he was the FIRST ever who had written an entire book SOLELY about the science of Hadith, hence he is referred to as the “first”, may Allah have mercy upon him.
His famous book:
Here a beautiful clip where a Kuweiti scholar proves the corruptness of the Rafidite sect and the proud of every Muslim when it comes to the science of Hadith (i.e. Al-Ramhurmuzi):