’Umar al-Khayy
m
(Muslim mathematician and poet):
’Umar ibn al-Khatt
b
(d. 644 (AH 23))
. Second caliph (
khal
fa
) and main architect of the Arab Islamic empire. Originally he was an enemy of Islam, but had a sudden conversion four years before the
hijra
. In
Mad
na,
’Umar's energy of will, piety, wisdom, and organizing ability made him second to the Prophet Mu
ammad in authority and prestige. The Prophet nicknamed him
faruq
, ‘distinguisher’ (between truth and falsehood). As second caliph (
khal
fa
) he organized the Islamic conquests and the administration of the empire. Traditions reveal, however, that he was feared rather than loved, and at the height of his power he was assassinated at Mad
na.
It was during ’Umar's caliphate that Muslim religious and political institutions arose which were to be the model for future generations. Among these were: the
d
w
n
(‘stipend register’), a form of welfare state by which annual stipends were paid to all Muslims from the public treasury; regulations for non-Muslim subjects (
dhimmi
); military garrisons which later became the great cities of Islam, e.g. K
f
and Fustat; the office of
q
i (judge)
; religious ordinances such as obligatory nightly prayers in the month of
Rama
n;
civil and penal codes; the hijra
calendar
; and the standardization of the text of the
Qur’
n