Muhaqqaq is a type of calligraphic script in Arabic

Arabic language

Arabic is a name applied to the descendants of the Classical Arabic language of the 6th century AD, used most prominently in the Quran, the Islamic Holy Book...

 derived from Thuluth

Thuluth

Thuluth is a script variety of Islamic calligraphy invented by the Persian Ibn Muqlah Shirazi, which made its first appearance in the 11th century CE . The straight angular forms of Kufic were replaced in the new script by curved and oblique lines. In Thuluth, one-third of each letter slopes, from...

 by widening the horizontal sections of the letters in the Thuluth script.

It was abandoned after the 16th century and only a very few panels and a number of Besmeles in hilya

Hilya

A hilya , hilye is a text describing the physical appearance of the Prophet Muhammad, often carried in a breast pocket...

s describing the virtues and qualities of Muhammad

Muhammad

Muhammad |ligature]] at U+FDF4 ;Arabic pronunciation varies regionally; the first vowel ranges from ~~; the second and the last vowel: ~~~. There are dialects which have no stress. In Egypt, it is pronounced not in religious contexts...

are to be found written in this script.