Great centers of religious learning were also centers of knowledge and scientific development. Such formal centers began during the Abbasid period (750-1258 A.D.) when thousands of mosque schools were established. In the tenth century Baghdad had some 300 schools. Alexandria in the fourteenth century had 12,000 students. It was in the tenth century that the formal concept of the Madrassah (school) was developed in Baghdad. The Madrassah had a curriculum and full-time and part-time teachers, many of whom were women. Rich and poor alike received free education. From there Maktabat (libraries) were developed and foreign books acquired. The two most famous are Bait al-Hikmah in Baghdad (ca. 820) and Dar al-Ilm in Cairo (ca. 998). Universities such as Al-Azhar (969 A.D.) were also established long before those in Europe.
Before Muhammad started to have the revelations and focus on preaching the word of God/Allah, he did had a profession. His profession was a merchant. He was a good merchant from what is known, and he had a good training for this profession since early age.
