(And it was not for the believers to go forth altogether) i.e., it was not appropriate or suitable for them to go out for military expeditions (Ghazw) all at once. Al-Kalbi narrated from Ibn Abbas (may Allah be pleased with both of them) that when the Almighty spoke severely against those who stayed behind, they said: "None of us shall ever stay behind from any army or detachment again." So they did so, and the Messenger of Allah (peace be upon him) remained alone. Then this verse was revealed: (And it was not...) until the end. The intended meaning is to prohibit them from going forth all together, for that causes a disruption in the pursuit of knowledge.
(Then why does not a group from every division of them go forth?) "Lawla" here is for incitement (Tahdid). When used with a past-tense verb, it serves as a rebuke for abandoning an action, and with a present-tense verb, it signifies a request and a command for it. However, the blame for abandoning an action that can be rectified may imply a command to perform it in the future. Meaning: Why did a Ta'ifah (a small group) not go forth from every Firqah (a large group)—such as the people of a town or a great tribe? Carrying the Firqah and Ta'ifah in this sense is derived from the context and the nature of the partitive "min" (from), as a part is generally smaller than the remainder. Otherwise, Al-Jawhari did not distinguish between them. Some have mentioned that Ta'ifah may apply to a single individual, while others say it does not, and that the minimum is two, or some say three.
(So that they may gain understanding in the religion) i.e., so that they may commit themselves to attaining Fiqh (understanding) in it. The form tafa''ul implies the effort to acquire something; the intention here is not the common meaning, but rather enduring hardship in seeking it, for it is difficult and cannot be achieved without diligence and struggle.
(And so that they may warn their people when they return to them, that they might be cautious [122]) i.e., cautious of that which they are warned against. The pronouns in "gain understanding" and "warn" refer to the remaining group understood from the discourse. Others have said that there must be an implicit estimation, meaning: "Why did a Ta'ifah not go forth from every Firqah, while another Ta'ifah stayed behind to gain understanding..." etc.
Although it would seem apparent to say "so that they may know" instead of "warn," and "understand" instead of "be cautious," the wording in this sublime arrangement was chosen to indicate that the teacher's purpose should be guidance and warning, and the learner's purpose should be the acquisition of fear [of Allah], not ostentation or arrogance.
The Proof of Islam, Al-Ghazali (may mercy be upon him), said: "In the first era, the name Fiqh was the name for the science of the Hereafter, the knowledge of the subtleties of the soul's afflictions and the spoilers of deeds, the power of encompassing the baseness of the world and the intensity of longing for the bliss of the Hereafter, and the dominance of fear over the heart. This verse points to that, so that by which warning and fear are instilled is Fiqh—not the definitions of divorce, emancipation, peace treaties, and leasing."
Farqad al-Sanji asked Al-Hasan about a matter and he answered him. He said: "The jurists (Fuqaha) disagree with you." Al-Hasan replied: "May your mother be bereaved of you! Have you ever seen a jurist? The jurist is only he who is ascetic in this world, desirous of the Hereafter, insightful in his religion, persistent in the worship of his Lord, pious, refraining from the reputations of the Muslims, chaste regarding their wealth, and a sincere counselor to their community." He did not say in all of that: "The one who memorizes the branches of legal opinions (fatawa)." This statement of Al-Hasan is excellent, yet what is common is to apply the term "jurist" to anyone who memorizes the branches absolutely, whether with their proofs or not, as in Al-Tahrir. In Al-Bahr, citing Al-Muntaqa, there is support for this. In Al-Qunyah, it is considered that memorization must be accompanied by proofs, so those who memorize without proofs do not enter into a bequest made to the jurists. From Abu Ja'far it is reported that he said: "The jurist among us is the one who has reached the ultimate goal in Fiqh; the mere mutafaqqih (the one pretending to be a jurist) is not a jurist, and he has no share in a bequest." It is apparent that what is considered in bequests and the like is the custom (Urf), which is what the speech of many of our scholars entails.
More than one has mentioned that the specification of "warning" is because it is the most important; otherwise, the intended meaning is general guidance, which includes teaching traditions, manners, obligations, and permissible acts, and warning is more specific than that. The claim that they are inseparable and that mentioning one dispenses with the other is negligence or feigned ignorance.
Many people have held that the meaning of "going forth" here is going forth to seek knowledge. Thus, the verse is not related to the preceding command of Jihad. Rather, after the Almighty explained the obligation of migration and Jihad—both of which are journeys for worship—He mentioned the other journey, which is migration to seek knowledge. Thus, the pronouns in "gain understanding" and "warn" refer to the mentioned Ta'ifah, which is the one that goes forth. This is what the speech of Mujahid requires; Ibn Jarir, Ibn al-Mundhir, and others narrated from him that he said: "Some of the companions of the Messenger of Allah (peace be upon him) went out into the deserts and found goodness from the people and abundance that they benefited from. They invited those they found of the people to guidance. The people said to them: 'We see that you have abandoned your companions and come to us.' They felt a sense of guilt regarding that, and all of them came from the desert until they entered upon the Prophet (peace be upon him). Then this verse was revealed: (And it was not...) until the end." That is: Why did some not go forth and some not stay behind, seeking goodness, to gain understanding in the religion, to hear what was revealed, and to warn the people when they returned to them?
It is deduced from this that seeking understanding in the religion is a communal obligation (fard kifayah). As for what is in Kashf al-Hijab regarding "Seeking knowledge is an obligation upon every Muslim," and its weakening by Al-Saghani, the meaning of "knowledge" there is nothing but that upon which the performance of obligatory duties depends. There is no doubt that learning this is an obligation upon every Muslim.
Some have mentioned that the verse contains evidence that the report of a single person (Khabar al-Ahad) is a proof, because the generality "from every division" implies that from every three people who are isolated in a village, a Ta'ifah should go forth to gain understanding to warn its people so they might remember and be cautious. If reports that were not mutawatir (mass-transmitted) were not considered, this would be of no benefit. Some have established the mode of evidence through two matters: First, that the Almighty commanded the Ta'ifah to warn, which necessitates the execution of what is commanded; otherwise, it would not be a warning. Second, His command to the people to be cautious upon being warned, because the meaning of His saying: (that they might be cautious) is "in order that they may be cautious." This also entails the necessity of acting upon the report of a single person. This evidence stands regardless of which of the two interpretations one chooses. The deduction from the verse for what was mentioned does not depend on the term Ta'ifah applying to one person—which is the beginning of numbers—but it suffices that it applies to whatever does not reach the limit of tawatur, even if it is three or more. Likewise, it does not depend on the hope/expectation not coming from the warners themselves, but rather from Allah the Almighty, intended metaphorically as a request, as is not hidden.