Imam an Nawawi said:
“the majority of Muslim scholars and leading authorities (al- muhaqqiqun wal-aktharūn) held that unless the Sahih is of the mutawātir category, it shall remain probable and can never attain the level of certainty”.
Imam al-Bayhaqi :
“The perspicuous scholars (Ahl al-nazar) among our [Ash`ari or Shafi`i] companions relinquish the use of lone-narrated reports as proofs in the divine Attributes if such reports do not have a foundation in the Qur'an or in scholarly consensus. Instead, they interpret them figuratively.”
Khateeb Al Baghdadi says:
“Khabar al-Āhād is where one of the conditions of mutawātir is missing even if a group narrated this report…they provide an obligation to act upon them, but are not obligatory of ‘ilm (do not provide certainty).”
Al Juwayni says:
“Akhbār āhād provide necessity for actions, but do not provide necessity in ‘ilm because a mistake is possible”.
in his first Usūl work al-Mankhul, written at the age of 26, said: "Some claim that Khabar ul-Ahaad imply certainty. This is impossible.” Many years later, in his other very famous work on Usūl (but not only other work on Usūl) he said in Al- Mustasfa: "Khabar Al-Ahaad does not imply certainty. This is a basic fact of its definition."
Ibn `Abd al-Barr
states in his book At-Tahmid (1:7) the position of the Ahl Us Sunnah Wal Jamaah: “What the majority of the people of knowledge believe is as follows: Some hold that the lone-narrated hadith make practice obligatory but not knowledge (yûjib al-`amal dûna al-`ilm). This is the position of al-Shafi`i and the vast majority of the jurists and the scholars of principles (Usūl ul-Fiqh). To them, the lone-narrated hadith does not make knowledge obligatory by itself and except on oath, providing definite preclusion of falsehood, and if there is no disagreement concerning it.”
Al Qurtubi said:
“The Ahkaam of the shariah can be taken by ghalabat ad-Dhann (preponderant knowledge), as is engendered by forms of Qiyas and Khabar Wahid.”
Imam Ibn Humām
said: “The majority of scholars and muhadditheen mentioned that Khabar al-Wāhid doesn’t provide certainty without other indications, and that with them it could provide ‘ilm but not necessarily indisputable certainty”.
Imam al-Suyuti in volume two of his book "The Precision in the Sciences of the Quran", comments in the chapter entitled `The Single and Odd Readings' that ahad reports , even if the narration is authentic, cannot be taken as an evidence in the matter of belief, or in the foundations of the deen (i.e. Islam); as the Quran is the source of the sources and is concerned with the creed, obliging belief in it, then tawatur becomes a condition for confirming it. Hence solitary reports will not be taken as evidence.
Imam Alaa’ al-Din al- Samarqandi
[d. 540 / 1145] (RH) said: “And from the āhād, if they are concerned with actions then they are a proof (Hujjah) but if they are concerned with ‘Aqeedah then they are not a proof (hujjah) for belief as they don’t give rise to certainty.”
Imam al Bazdawi
(RH) said: “The Wahid provides necessity in actions but not with ‘ilm (certain knowledge), and we explained that mashoor doesn’t provide ‘ilm, so āhād or Wahid certainly does not. The Wahid does, however, have possibility and he who denies this has misguided his mind and himself.”
Abul Hussain Hassani, on 01 January 2013 - 10:39 AM, said:
I heard from some brothers that member 'Hannibal' himself doesn't belief in Hadith Science, Shia or Sunni. So how can such a person, who rejects Hadith Science, write article in refutation of Sunni Hadith Science. Strange!
He never said he didn't believe in hadith science,he said that khabar ahad as well as rijal does not bring yaqeen.
Also to answer your question,someone can say to you that X person is not a christian,yet he is still refuting it. So your statement isn't sensible.