Ibn ‘Abbaas (radiyallaahu-anhumaa) said:

“Do not sit with the people of desires (i.e. people of bidah), for indeed their gatherings cause sickness in the hearts.”

[Al-Ibaanah 371]

Imaam Ahmad (rahimahullaah) said:

”It is neither permissible for anyone to sit with ahlul bidah nor mix with them, nor socialize with them.”

[Source: Al-Ibaanah 495]