To acquire knowledge under the expertise and guidance of a fully qualified ʿĀlim of Dīn is absolutely essential. Failure to do so generally results in absolute guidance. This has been the practice of our pious predecessors and even the Ambiyā عليهم السلام.
The Qur’ān was revealed by Allāh as a guidance and a means of knowledge for mankind but without the explanation of the Messenger of Allāh ﷺ the meanings would inevitably be misunderstood.
During the era of the Tābi’īn, whenever anyone would claim to have any knowledge, he would be asked as to whom he acquired that piece of knowledge from.
Imām Mālik رحمه الله was once asked if knowledge can be acquired from one who did not sit in the company of the ʿUlamā and instead he sufficed with, and depended only on books. Imām Mālik رحمه الله replied in the negative and said, “Knowledge should not be acquired except from one who has memorised, accompanied scholars practiced upon his knowledge and processes piety.” [Ādāb Al-Ikhtilāf, Page 145].
Sheikh Muḥammad ʿAwwāmah mentions in his book ‘Ādāb Al-Ikhtilāf’, “The ʿUlamā never used to pay attention to the one who did not have an ustādh, neither would they consider such a person even worthy of being spoken to in matters of knowledge due to him being prone to mistakes.”
He further writes, “Qādī ʿIyāḍ and others have narrated that when Imām Aḥmad ibn Ḥanbal رحمه الله was requested by the ruler of his time to discuss a certain matter with Ibn Abī Duʿād, Imām Aḥmad رحمه الله turned his face away and said, “How can I converse with a person whom I have never seen at the door of any ʿĀlim?” [Ādāb Al-Ikhtilāf, Page 144].
This proves that merely relying on the study of books without the supervision and mentoring of a fully qualified teacher is incorrect and has never been acceptable in the tradition of Islamic knowledge.
Imām ash-Shāfiʿī رحمه الله says:
أخي لن تنال العلم إلا بستة، سأنبيك عن تفصيلها ببـيان
ذكاء، وحرص، واجتهاد، وبلغة، وصحبة أستاذ، وطول زمان.
My brother, you will never acquire knowledge without the following six essentials: intelligence, desire, effort, poverty, the tuition of an ustādh, accompanied by a long consistent period (of studying under him).