The classical era of ijtihad, which lasted for about 250 years (632–875), was a period of astounding jurisprudential research and creativity. A critical awareness of this period is valuable for understanding contemporary ijtihad. The classical period underscores a simple but powerful thesis that Islamic law is inherently dynamic and diverse, responsive to customs, cultures, and commerce, and to the diversity of nations, communities, and global conditions. The classical era also demonstrates that God's Law animates the physical universe and systems of knowledge on a daily basis. Islamic law in all times and in all places must, therefore, proactively respond to changing realities under the guidance of the Basic Code. Any assertion that the Basic Code alone can answer all legal questions is as unsustainable, as is the counter-assertion that the Basic Code is irrelevant to the technological intricacies of contemporary life.

The classical era of ijtihad is closely related to, but distinguished from, the period of prophecy (610–32) during which the Qur'an was received and the Prophet's Sunnah was delivered. The classical period may be counted from 632, the year the Prophet passed away, to 875, the year when the five founders of madhabs (Islamic schools of jurisprudence), Sunni and Shia, had launched their teachings and passed away. All the founders of the five madhabs were born and died during the classical period. Abu Hanifa, the founder of the largest Sunni madhab, and the most senior Sunni opiniojurist, died in 767.