It's meaning: What is meant by Guidance in this context, is the explanation of Islamic rules1 (ahkam) to the ignorant. Thus it is obligatory upon the scholar (one who knows) (alim) to guide the ignorant and to teach him the [different] issues of faith. It is due to this that the Precept is sometimes known as 'the obligation of informing (i'lam) the ignorant by the scholar.'
The source: It is possible to demonstrate the Precept by the following:
I. The Verse: His words, the most High; "And it does not beseem the believers that they should go forth all together; why should not then a company from every party from among them go forth that they may apply themselves to obtain understanding in religion, and that they may warn their people when they come back to them that they may be cautious?"2 This indicates the obligation to teach the rulings (ahkam) in order to warn (admonish-indhar), and to guide those who do not know. Thus it becomes obligatory for the scholar to guide the ignorant in accordance with the obligatory nature of the noble verse. It should be clear that the verse is elucidating the objective of warning (admonishing). What this means is that the admonition is the end result for seeking in-depth understanding (al-tafqquh), thus only then can the obligation of guidance be attained. The verse however does not allude to the attainment of knowledge by the one being admonished, in other words the physical achievement of guidance by the one being admonished will not falter with the obligation of seeking in-depth knowledge for the sake of guidance by the one who admonishes.
As is stated by al-Sayyid Abu al-Qasim al-Khui: as for the general theological principles, there is no doubt in the obligation of teaching them to the one who is ignorant of them due to the obligation of conveying the Islamic rules (al-ahkam al-shar'iyyah) to the people, generation after generation until the Day of Judgment. This is indicated by the previous verse, and [many] reports are found regarding assertion in relation to knowledge, its teaching and learning.3
II. The Evidence of Necessitating the Conveyance of the Islamic law (Adillah al-Tabligh): There is no doubt regarding the obligation of conveying the religious rules (al-ahkam al-shar'iyyah) upon the extent of sufficiency (' ala hadd al-Kifayah)4 in order to preserve and maintain the Shari'ah, this matter is regarded from among the necessities of faith.