It is well worth reading: “Introduction to the beginnings of the Hadeeth sciences: Mutawaatir, Aahaad, and their categories (Part 3)” before this article, since this is an additional note to the topic of Al-Ghareeb classification in hadeeth that was mentioned in that article.
Shaikh Abdullāh Ibn Abdur-Raheem Al-Bukhāree (hafidhahullāh) said regarding the Ghareeb Hadeeth:
It has been reported from the majority of the scholars from the Salaf that they would praise the Mash-hoor hadeeth narrations and they would dispraise the Ghareeb narrations in general. Because the rare or singularly reported (ghareeb) narrations are prone to error and suspicion (see Majmoo` al-Fataawa of Ibn Taymiyyah, 18/39). And this is different to the hadeeth which are mash-hoor (i.e. narrations with three or more narrators at each level of the chain of narration) because they are further away from being erroneous in general.
Al-Haafidh Ibn Rajab (rahimahullaah) said:
“The Salaf would praise the mash-hoor hadeeth, and they would in general dispraise the ghareeb narration – and from that is the saying of Ibn al-Mubaarak (d.181H): ‘Knowledge is that which comes to you from here and there, meaning it is mash-hoor.’
It is reported from Maalik (d. 179H) that he said: ‘The worst of knowledge is the ghareeb (rare and lone reports). The best of knowledge is that which manifest that which is narrated by the people.’
Muhammad Ibn Jaabir reported from Al-A`mash from Ibraaheem who said: ‘They [the Salaf] would dislike the ghareeb hadeeth and ghareeb speech.’
It is narrated from Abu Yoosuf that he said: ‘Whoever seeks after the ghareeb hadeeths, lies!'”
(Sharh `Ilal at-Tirmidhee 2/621-4, and see Al-Kifaayah, 223-226)
So based upon that, we say: A ghareeb hadeeth can be saheeh, rather it can even be of the utmost level of authenticity, and it can also be other than that.
Al-Haafidh Ibn As-Salaah (rahimahullaah) said:
“Thereafter the ghareeb narration is divided into (1) the saheeh such as the singular reports which have been reported in the Saheeh [of al-Bukhaaree], and (2) those that are not saheeh, and they are most of the gharaa’ib (singularly reported narrations).”
(Ma`rifat Anwaa`i `ilmil-Hadeeth, p. 270-71; and see Al-Muqni` 2/441; Al-Hidaayah 1/308)
Al-Haafidh an-Nawawee (rahimahullaah) said in Sharh Muslim (1/43):
“When one proceeds to follow up and examine the singularly reported narrations, then the narrator is in one of four situations:
1. A state wherein the narrator opposes a narration of one who is a better memoriser than himself. So therefore that narration is da`eef (weak) or munkar (denounced).
2. That the narrator does not oppose another narrator in what he reports. And the narrator is a haafidh (sound memoriser), daabit, mutqin (precise in his narrating), then his report is saheeh.
3. That the narrator is deficient in this (i.e. no. 2 above) but he is close to his level, then such a report is hasan (good/acceptable).
4. One whose condition is far removed from the above (i.e. no. 2) so he becomes shaadh (contradictory), munkar (denounced) and mardood (rejected).”
For each of these situations there are details which I have clarified in my detailed explanation of “Al-Mawqidhah” and “An-Nukhbah” – may Allaah facilitate their publication.