Ibn Hajar al-Asqalani
ابْن حَجَر العَسْقَلَاني
The greatest hadith scholar of the later period
Ahmad ibn Hajar al-Asqalani wrote Fath al-Bari — a 13-volume commentary on Sahih al-Bukhari — and Bulugh al-Maram, studied by millions of Muslims to this day.