bidʿah

Delving into Falsehood (I’ll take what’s good)

It is reported that Ibrāhīm b. Ad-ham – Allāh have mercy on him – said:

Delving into falsehood removes the ability to recognize the truth from the heart.

Abu Nu’aym, Hilyatu Al-Awliyā` 8:22.

Followers of Dajjal

It is reported that Muhammad b. Sīrīn – Allāh have mercy on him – said:

If the Dajjāl appears, I believe the heretics (People of Desires, Bid’ah) will follow him.
Al-Lālakā`ī, Sharh Usūl I’tiqād Ahl Al-Sunnah 1:131

Rubbish Opinions

Mālik b. Mighwal said:

Al-Sha’bī once said to me, “When these [people] report to you from Allāh’s Messenger – praise and peace of Allāh be upon him, adhere to it; but when they merely opine, throw it in the trash.”

Al-Dārimī, Al-Sunan 1:78.

From whom does Knowledge Come?

It is reported that ‘Abdullāh b. Masʿūd – Allāh be pleased with him – said:

The people will remain upon goodness as long as knowledge comes to them from the Companions of Allāh’s Messenger – Allāh’s praise and peace be upon him, and from their seniors. But when knowledge comes to them from their minors, that is when they will be destroyed.

Ibn ‘Abd Al-Barr, Jāmi’ Bayān Al-‘Ilm wa Fadlihi article 1060.

Note
Being upon a good and right path is based on following the knowledge of the Companions and seniors: scholars and people who adhere to the Sunnah, whereas taking knowledge from minors like ignorants and heretics is a sign of destruction.

The Sly Heretic [Bidah]

It is reported that Mufaddal b. Muhalhal – Allāh have mercy on him – said:
If the heretic started mentioning his bid’ah right at the beginning of the sitting, you would be on your guard and flee from him, but what he does is begin by mentioning ḥadīth from the Sunnah. Then, he slips his bid’ah in on you. It might then stick to your heart; but when will it leave your heart?

Ibn Battah, Al-Ibānah Al-Kubrā, 2:444.