It is imperative for the learner that he leads others to adorning himself with trustworthiness in knowledge questing, action, and transmission. Indeed the success of this Ummah lies with the correctness of its actors; the success of its actors lies with correctness of its knowledge; the correctness of its knowledge demands that its men (of knowledge) are trustworthy in what they narrate and describe. Whoever speaks with respect to knowledge without trust has smeared it with dirt and placed a stumbling block on the path of the success of the Ummah.
So, do not mix with people who ascribe themselves to knowledge; who learn but not to put the best of character into actions, or to benefit people with what they know of wisdom. You will never find trust in the likes of those. These are the people that say what they have not heard or describe what they do not know.
This is what has invited the erudite scholars into criticising certain men.
[Therefore] being truthful in speech is a sign of reverence, dignity, clarity of the inner soul, loftiness of determination, soundness of the intellect, an inviter to people’s love, source of people’s success and a protection for the Deen. This is why it is an individual obligation [to be always truthful]. What loss is the lot of whoever has failed in this wise! Whoever is untruthful has caused his soul and knowledge [many] harm.
[Al-Imâm] Al-Auzâ’î said: ‘Learn truthfulness before knowledge.’
[Al-Imâm] Waqee’ said: ‘This knowledge, none will rise in it except the one that is truthful.’
So, learn truthfulness before knowledge.
Truthfulness is saying things the way they are, upon the [correct] thought. The path of truthfulness is one, unlike lie which is of varieties and colours.
Adapted from Hilyah Tâlib AL-Ilm of Shaykh Bakr Abu Zayd, Point Thirty-Two and Thirty-Three