The belief in the Messenger Muhammad PBUH obliges that we obey and follow him. And it obliges us to educe Islam, in terms of ‘aqīdah (creed) and rules, from his Sunnah. Allah  said:

And He  said:

And He  said:

However, to seek inference from the Sunnah varies depending on the subject matter on which inference is required. If the matter on which inference is sought is considered probable (Ghalabatu zann), then information about it is sought on the basis of what the Messenger  most probably said. By greater reason, we seek information about it on the basis that the narrator is certain of what the Messenger  said. In matters requiring decisiveness and certainty, any inference about it must come from what the narrator is certain about what the Messenger  said. Such matters are not educted by what the Messenger  most likely said, this is because the speculative (Zann) evidences are not considered to be sound enough for establishing certainty (Yaqeen).

It is sufficient for a person to think of the Hukm Shar’i that this is probably the Hukm of Allah  and then he is bound to follow it as a Hukm. Therefore it is allowed for the evidences (dalīl) to be speculative (zanni); whether it is speculative (zanni) with regards to their authenticity or meaning.

The Messenger accepted it in judicial cases and called for its acceptance in the sayings of his Ahadith; the Sahaba  also accepted it in their observance of the Shar’i rules. Furthermore, the ‘aqīdah (creed) is decisive, agrees with reality and is supported by evidence. This is the nature of the ‘aqīdah, so such evidence should produce decisive acceptance, and this would not happen unless the evidence itself is decisive. Probable (Zanni) evidence cannot be decisive. Therefore the solitary report (Khabar al Ahad) is not a suitable evidence for the ‘aqīdah because it is based on probability, whereas the ‘aqīdah must be certain and free of doubt. Allah  in the Noble Qur’ān has rebuked the following of speculative knowledge (zann). He  said:

And He  said:

And He  said:

And He  said:

And He  said:

These and other verses in the Qur’ān explicity rebuke those who follow speculation (Zann) in the creed (Aqa’id) of Islam. These rebukes are evidences of the prohibitions of following speculation (Zann). The solitary report (Khabr al-Ahad) is speculative evidence, so taking this as evidence in the ‘aqīdah is a matter explicitly rebuked in the Qur’ān. Thus the Shar’i evidence and the reality of the ‘aqīdah itself indicates that deduction from speculative (Zanni) evidence does not oblige belief in what this evidence brings. Thus the solitary report (Khabar al-Ahad) is not a proof for the ‘Aqa’id. The above-mentioned verses have been explicitly restricted to the ‘Aqa’id and not the Shar’i rules because Allah  determined the following of speculation (Zann) in the creed as misguidance (Dhalal) and he  clearly reproached those who follow speculation in the ‘Aqa’id.

He  said:

This indicates that the matter in concern is the ‘Aqa’id.

Allah  says:

So He  defined the Dhalal as Kufr, which happens after following conjecture (Zann) in belief. Thus, this indicates that the subject matter of the ayat is the ‘Aqa’id. From another angle, it has been established that the Messenger  judged using the solitary report. In his time, the Muslims accepted the Hukm Shar’i by the solitary report (Khabar al-Ahad) and he  accepted that. Thus the Hadith of the Messenger  specified these verses in other than Hukm Shar’i i.e. in the Aqa’id. Therefore, the Hadith of the Messenger excluded Hukm Shar’i from the verses on the assumption that some of the verses are general (‘Aamm) in form.

As for what has been reported about the Prophet  that he sent single envoys to the rulers and single messengers to his 'Amils and what has been reported that the Sahabah  used to accept the saying of a single Messenger in informing them of the Sharī’ah rule such as (the order to) face the Ka'ba, the order prohibiting alcohol, the Messenger's  sending of 'Ali  to the people to read to them sura 'al-Tawba' and so on. This does not indicate the acceptance of the khabar al-ahad in ‘aqīdah but the acceptance of khabar al-ahad in conveing (tabligh) the Dawah, whether in conveying the Sharī’ah rules or conveying Islam itself. It should not be claimed that accepting the conveyance of the message of Islam is a conveyance of the ‘aqīdah. Since accepting the conveyance of Islam is an acceptance of a report and not the acceptance of ‘aqīdah. As evidenced by the fact that the one to whom a report is conveyed must use his intellect regarding that which has reached him. If decisive evidence is established for him upon it, he should believe in it and he will be accounted if he disbelieves in it. Thus, the rejection of a report about Islam is not considered kufr, but the rejection of Islam for which the decisive evidence has been established for him is what is considered to be an act of kufr. Therefore, conveying Islam is not considered part of ‘aqīdah. There is no dispute about the acceptance of a report of a single person in conveyance. All the reported incidents indicate that spreading the message constituted either the conveyance of Islam, Qur’ān or the rules. As for the conveyance of ‘aqīdah, there is no evidence for educing it from the khabar al-ahad.

Therefore, the evidence of the ‘aqīdah must be certain, i.e, definite evidence. Because the ‘aqīdah is definitive and decisive. It is not definitive or decisive unless derived from definite evidence. Therefore, the evidence must be Qur’ān or Hadith mutawatir such that both are definite in meaning. It has to be taken in ‘aqīdah and Sharī’ah rules. The one who rejects it is charged with kufr as well as the one who denies what it indicates, whether it is a belief or a Sharī’ah rule.

However, if the evidence is based on a solitary report (Khabar al-Ahad), then it would not be definite (Qat’i). If it is sound (Sahih) then it would indicate high probability and the creed (‘Aqa’id) brought by it would be accepted as speculative, but not as definite. It is not permitted to believe in such ‘Aqa’id as it would not be decisive. This is because ‘aqīdah is a matter of decisiveness and certainity, while the solitary report (Khabar al-Ahad) only indicates probability. The one who rejects the solitary report (Khabar al-Ahad) is not considered a Kafir. However it is not allowed to belie it because if it was allowed to belie it then it would be allowed to belie all the Ahkam Sharī’ah inferred from the speculative (zanni) evidences, a matter of which no Muslims ever talked about.

In the same way a Hadith may be narrated as Khabar al-Ahad and vice-versa, but this method of narration would negate the necessity of accepting and believing in this Hadith. However, it is accepted as a Hadith and it is obligatory to take from what it came with as Hukm Shar’i.