Every 100 hijriyy years Allah brings a Mujadid. The Mujadid refutes the false accusations against Islam and eradicates the suspicions of its people by his teachings and authority or only by his teachings.
‘Umar bin ‘Abdul ‘Azeez was the 1st Mujadid on the top of the first hundred years. He had both. He destroyed innovations and misguided beliefs, erased injustices and tyranny and compensated those who were wronged and mistreated.
These things endured among Muslims for tens of years before him. Among them cursing Imam ‘Aliyy on the minbar posts by Shaykh personalities appointed by Bani Ummayah. He uprooted this practice.
Likewise, he rebuked the false claims of the misguided innovators like Ghaylaan from Damascus who was then the Mu’tazilah’s head. After learning about Ghaylaan’s call to this faction’s dogmas, ‘Umar bin ‘Abdul ‘Azeez summoned him and told him to retract and repent. He showed that he repented. Otherwise, had he continued straying ‘Umar bin ‘Abdul ‘Azeez would have persecuted him.
After this Pious Caliph came Imamush Shafi’iyy who served Islam immensely. He used to disprove the innovators and dismiss their doubts and delusions which they raised against Ahlus Sunnah. He enlightened the Muslims by the Islamic ijtihaad Allah bestowed on him and straightened a lots of crookedness and removed them.
Afterwards Ibn Surayj ashShafi’yy came on the top of the 3rd century.
In the beginning of the 4th century a pious, God-fearing and great scholar called Sahl bin Muhammad bin Sulayman came.
Then many other Mujadid personalities on the top of their centuries came and benefited Muslims and served Islam by Allah’s Will.
It is not a condition that the Mujadid should have authority, rather he would be a man of righteousness and piety or both. He could be also a person of knowledge without authority like Imamush Shafi’iyy who was never appointed as a judge not to mention been given a ministerial position.
The same applies to Imam Abu atTayyib Sahl bin Muhammad who did not engaged in any ministry or judge duties. Ibn Surayj, however, was a judge and a pious ‘aalim.
The Mahdiyy, on the other hand, will combine the two: having authority and piety with vast knowledge.
May Allah make us and Muslims benefit from those people with such high caliber.