Maulana Faisal Ahmad Sahib Nadvi Bhatkali writes:

Our pious predecessors (Ulema-e-Salaf) did not give any importance to mere bookish knowledge; meaning, if a person did not have teachers (Asatiza) and mentors (Mashaikh) and had acquired some knowledge only from books, it was not given any weight. There have been some people in Islamic history whose mention in books appears with condemnation rather than greatness. The pious predecessors were not even willing to engage in scholarly debate with someone possessing such absolute bookish knowledge. What an exemplary incident Qadi Ayyad (may Allah have mercy on him) has narrated: that during the time of Imam Ahmad (may Allah have mercy on him), there was a man named Ibn Abi Dawood who possessed only bookish knowledge, and he used to raise controversial debates here and there. The Caliph of the time, Mu'tasim, said to Imam Ahmad: "Please speak with Ibn Abi Dawood and silence him." Imam Ahmad replied: "How can I speak to a person whom I have never seen at the doorstep of any scholar (Alim)?" Reflect and take heed of how people are causing various tribulations (Fitnah) today with such bookish knowledge.