Imām Mālik (رحمه الله) said:[1]
Knowledge is not taken from four:
—A fool who makes an open display of his foolishness
—A person of desires who calls to it (i.e. innovation)
—A man known to lie regarding people’s speech, even though he does not lie upon the Messenger (صلى الله عليه وسلم)
—A man of virtue and excellence who does not know (the veracity or authenticity) of what he is narrating.
Knowledge is carried in the vessels that are human hearts, and the hearts have certain states that affect and undermine the veracity and integrity of knowledge and its tranmission. This can be likened to a bucket with holes, or a bucket with contamination. Water transported in such a bucket will be lost or tainted.
From these states is foolishness (frivolity), and a fool is a silly person who lacks judgement and sense, hence, he cannot be entrusted with the weighty affairs of religion.
From them is the person of innovation, his reports, particular those that relate to his innovation, remain suspect due to the presence of bias and a motive to swerve from honesty.
From them is the man who lies regarding the speech of people, even if he does not lie upon the Messenger (صلى الله عليه وسلم). This person remains suspect, since if he does not beware of lying upon people, then doubt is cast, about his narrating in affairs of religion, and this is a safety mechanism.
From them is the righteous man who is heedless and does not pay attention about the veracity of what he narrates. So he is not like the others, having neither foolishness, desires, nor lying, but he falls short. So as a protective mechanism, knowledge is not taken from him either.
This type of wisdom from the great scholars of the Muslims is indicative that this religion has been preserved. The Qur’ān is preserved (15:9-), the Prophetic Sunnah is preserved, and the mode of transmission of religious knowledge has been confined only to those who combine sound creed, uprightness, truthfulness and precision, thereby eliminating error, concealment, distortion and alteration, all of which the People of the Book fell into.