Hadith 1: 

عن محمد بن مسلم قال: قال أبو عبد الله ع‌ يا محمد ما جاءك في رواية من بر أو فاجر يوافق القرآن فخذ به، و ما جاءك في رواية من بر أو فاجر يخالف القرآن فلا تأخذ به‌

Narrate tht Abu Abd-Allah Imam Sadiq (عليه السلام) said to Muhammad bin Muslim:

"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."

[Source: Tafseer al-Ayyashi, Vol. 1, Pg. 9]

Hadith 2:

عن الحسن بن الجهم عن العبد الصالح ع قال‌ إذا كان جاءك الحديثان المختلفان- فقسهما على كتاب الله و على أحاديثنا، فإن أشبههما فهو حق و إن لم يشبههما فهو باطل‌

Narrated that Abd al-Saleh Imam Kazim (عليه السلام) said,

"If two conflicting Hadith come to you, then evaluate them based on the Book of Allah and on Our traditions (Ahadith). If it is similar to them, then it is true, but if it is not similar to both of them, then it is false."

[Source: Tafseer al-Ayyashi, Vol. 1, Pg. 9]

Hadith 3:

محمد بن يحيى، عن عبد الله بن محمد، عن علي بن الحكم، عن أبان بن عثمان عن عبد الله بن أبي يعفور، قال: وحدثني حسين بن أبي العلاء (1) أنه حضر ابن أبي يعفور في هذا المجلس قال: سألت أبا عبد الله 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 (2) وإلا فالذي جاء كم به أولى به

Narrated from Husain ibn Abi al-Aala that I asked Abu Abd-Allah Imam Sadiq (عليه السلام) about the differences in Hadith which is narrated from people whom we trust and also from other people we do not trust." 

The Imam (عليه السلام) 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?) "

[Source: al-Kafi, Vol. 1, Pg. 69]

Hadith 4:

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)."

Hadith 5:

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.’"