It is reported that Al-Fudayl b. ‘Ayyâd – Allâh have mercy on him – said:
Verily, Allâh has angels who seek out the circles of remembrance [of Allâh], so be careful who you sit with; make sure it is not with an adherent of bid’ah, for Allâh does not look at them. And the sign of nifâq (hypocrisy in faith) is that a man mingles with an adherent of bid’ah.
Ibn Battah, Al-Ibânah Al-Kubrâ 1:460
Taken from: http://www.sayingsofthesalaf.net/