Authentication of Hadees
1) Tafseer Al Ayyashi - Chapter on the abandonment of Hadees that is contradictory to the Quran
عن محمد بن مسلم قال: قال ابوعبدالله (عليه السلام): يا محمد ما جائك في رواية من بر أو فاجر يوافق القرآن فخذ به، وما جائك في رواية من بر او فاجر يخالف القرآن فلا تأخذ به
Abu Abdillah (as) said:
"O Muhammad, whatever comes to you in a narration from a righteous person or an immoral person that agrees with the Quran, then take hold of it. And whatever comes to in a narration from a righteous person or an immoral person that contradicts the Quran, then do not take hold of it."
2) Al Kafi : The Book on Virtue of Knowledge : H 197, Ch. 22, h2
Muhammad ibn Yahya has narrated from ‘Abd Allah ibn Muhammad from Ali ibn al-Hakam from Aban ibn ‘Uthman from 'Abd Allah ibn abu Ya‘fur who has said the following.
أنه حضر ابن أبي يعفور في هذا المجلس قال: سألت أبا عبدالله (عليه السلام) عن اختلاف الحديث يرويه من نثق به ومنهم من لا تثق به؟ قال إذا ورد عليكم حديث فوجدتم له شاهدا من كتاب الله أو من قول رسول الله (صلى الله عليه وآله) وإلا فالذي جاء كم به أولى به
"In a meeting where ibn abu Ya‘fur was also present I asked Imam abu ‘Abd Allah (DivineSupremeCovenantBody) about the differences in Hadith which is narrated from people whom we trust and yet from other people we do not trust." The Imam replied, "If you come across a Hadith and you find evidence in the Holy Quran to support it or in Hadith of the Holy Prophet (you may follow it), else the one who has come with the narration is more deserving of it. (i.e. leave the narration to the one who has brought it to you?) "
3) Rejaal al-Kashi, p.195
Imam Sadiq (a.s) concerning al-Moghira Ibn Sa`eed said:
"Verily, al-Moghira Ibn Sa`eed interpolated in the Hadith books of the companions of my father. He added things that my father had not said. Thus, fear Allah and do not accept anything (claimed to be) from us that contradicts the Words of our Lord and the Tradition of our Prophet Muhammad (P)."
4) Rejaal al-Kashi, p.195
Younus Ibn Abdul-Rahman said: “I met many people in Iraq who had met Imam Baqir and Imam Sadiq (peace be upon them). I heard their narrations and copied their books. Then when I met Imam Redha (a.s) I presented them to him. He denied many of those narrations and said: ‘Surely, Abul-Khattab fabricated in the name of Imam Sadiq (a.s). May the curse of Allah be upon Abul-Khattab and his followers who interpolated these narrations to this day in the books of the companions of Imam Sadiq (a.s). Do not accept anything (claimed to be) from us against the Quran.’"
The above Hadees are in conformity with the following verse of the Holy Quran which is used as a supporting argument for Ilm Ar Rijal according to which we cant just reject a Hadees because of lack of trustworthiness of the narrator:
Quran; Sura 49, Verse 6:
يَا أَيُّهَا الَّذِينَ آمَنُوا إِنْ جَاءَكُمْ فَاسِقٌ بِنَبَإٍ فَتَبَيَّنُوا أَنْ تُصِيبُوا قَوْمًا بِجَهَالَةٍ فَتُصْبِحُوا عَلَىٰ مَا فَعَلْتُمْ نَادِمِينَ
"O ye who believe! If a wicked person comes to you with any news, ascertain the truth, lest ye harm people unwittingly, and afterwards become full of repentance for what ye have done."
Hence as per the above verse we are to check for certinity of a Hadees even if the narrator is not trustworthy and cannot just brush aside the Hadees because of the lack of trustworthiness of the narrator.
The same has been emphasized by Yaqub Al Kulayni the author of Al-Kaafi. He says in the introduction of Al-Kaafi:
"My brother, may Allah guide you, indeed it is not possible for anyone to differentiate (Tamyeez) in the least on the basis of his own speculation between the narrations of the scholars regarding which there is a disparity in transmission (Riwaayah). This can only be done by following what the Sagacious, on him be peace, has said: “Examine it by the Quran, whatever corresponds to the book of Allah, take it: (however) whatever opposes the book of Allah, reject it.” He, on him be peace, also said: Leave aside that which the people agree with, for indeed Guidance lies in opposing them”. He (further) said: Accept that on which there is consensus (mujma’ ‘alayh). For indeed there is no uncertainty (Laa Raib) in that which there is a consensus (of masomeen a.s.)"
Another Narration which does not permit one to reject a narration attributed to the Imam's (as):
حدثنا محمد بن الحسين عن محمد بن اسماعيل عن حمزة بن بزيع عن على السنانى عن ابى الحسن ع انه كتب إليه في رسالة ولا تقل لما بلغك عنا أو نسب الينا هذا باطل وان كنت تعرفه خلافه فانك لا تدري لم قلنا وعلى أي وجه وصفة.
Muhammad b. al-Husayn narrated to us from Muhammad b. Isma`il from Hamza b. Bazi from Ali the as-Sinani from Abu ‘l-Hasan (as) that he wrote to him in an epistle,
"And do not say for what reaches you from us and is attributed to us “this is false” even if you have known its opposite, for verily you do not know why we said (it) and upon which aspect and attribute."
[Source: Basair Al-Darajat Pg. 538]