Praise be to Allah.
If what is meant by Raafidi is one who regards the two Shaykhs Abu Bakr and ‘Umar (may Allaah be pleased with them) as kaafirs and disavows them, and believes in the tenets of kufr that are to be found in many of the books of the Raafidi Ithna ‘Asharis, then the reports of such a person cannot be accepted and there are no reports from such people in al-Saheehayn at all.
Al-Haafiz Ibn Hajar (may Allaah have mercy on him) said:
Shi’ism as known in the early days of Islam is the belief that ‘Ali was superior to ‘Uthmaan, and that ‘Ali was in the right in his wars and that those who differed with him were wrong, whilst giving precedence to the two Shaykhs [Abu Bakr and ‘Umar] over ‘Ali and regarding them as superior. Some of them may have believed that ‘Ali was the best of creation after the Messenger of Allaah (peace and blessings of Allaah be upon him). If a person was like that but was pious, religious and sincere, and based his view on what he thought was right, then his narrations are not to be rejected for that reason, especially if he did not propagate these ideas.
As for Shi’ism as it was known later on, it is pure rafd (rafd is the idea that Abu Bakr and ‘Umar are to be disavowed and are not Muslims), and the reports narrated by an extreme raafidi are definitely not to be accepted.
Tahdheeb al-Tahdheeb (1/81)
Imam al-Dhahabi (may Allaah have mercy on him) said:
Bid’ah is of two types: minor bid’ah such as Shi’ism without exaggeration or deviation. This was the case with many of the Taabi’een and the generation that followed them, although they were religiously committed, pious and sincere. If the ahaadeeth of these people were rejected, many reports from the Prophet (peace and blessings of Allaah be upon him) would be lost, and that is obviously a bad thing.
Then there is major bid’ah, such as complete rafd and exaggeration therein, and undermining the position of Abu Bakr and ‘Umar (may Allaah be pleased with them), and promoting such ideas. Reports narrated by such people are definitely not to be accepted.
Moreover, I do not know of anyone among that type of Shi’ah nowadays who is sincere or trustworthy. Rather lying is their slogan and taqiyah (dissimulation) and hypocrisy are their shield. How can the narration of such a one be accepted? No, definitely not.
The extreme Shi’i at the time of the salaf, as known to them, was one who spoke against ‘Uthmaan, al-Zubayr, Talhah, Mu’aawiyah and some of those who fought against ‘Ali (may Allaah be pleased with him), and reviled them.
The extreme Shi’i in our time, as known to us, is the one who regards these leaders as kaafirs and also disavows the two Shaykhs [Abu Bakr and ‘Umar]. Such a one is misguided and lost.
Mizaan al-I’tidaal (1/5-6)
But if what is meant is Shi’i narrators who preferred ‘Ali ibn Abi Taalib to ‘Uthmaan, or to the two Shaykhs Abu Bakr and ‘Umar (may Allaah be pleased with them), without reviling them or disavowing them, or holding other beliefs of kufr which are stated in many of the books of Ithna ‘Ashari Shi’ah, then there are reports from such narrators in al-Saheehayn and elsewhere, and the muhaddithoon accept their hadeeth if they are known to be truthful, to have good memories and to be trustworthy. Al-Haafiz Ibn Hajar collected in Hadyi al-Saari the names of all those who were known as Shi’ah among the narrators of al-Bukhaari, and a number of contemporary scholars have written about the methodology of the authors of al-Saheehayn [i.e., al-Bukhaari and Muslim] in dealing with the Shi’ah narrators. Among these references are the following:
1 – Manhaj al-Imam al-Bukhaari fi’l-Riwaayah ‘an al-Mubtadi’ah min Khilaal al-Jaami’ al-Saheeh: al-Shee’ah Unmoodhajan. By Kareemah Sudani. Maktabat al-Rushd, Riyadh.
2 – Manhaj al-Imamayn al-Bukhaari wa Muslim fi’l-Riwaayah ‘an Rijaal al-Shee’ah fi Saheehayhima by Muhammad Khaleefah al-Shara’, Jaami’at Aal al-Bayt, 2000 CE.
3 – Diraasaat fi Manhaj al-Naqd ‘an al-Muhadditheen by Muhammad al-‘Umari, Dar al-Nafaa’is, ‘Ammaan, 2000 CE. This contains a discussion of al-Bukhaari and his narration from innovators, pp. 105-109
4 –Manhaj al-Naqd ‘inda al-Muhadditheen, by Akram al-‘Umari, p. 39
And Allaah knows best.