What is the Islamic ruling on the Rāfiḍha and how should we interact with them?

Shaykh Rabīʿ ibn Hādī al Madkhalī:

I assume that the questioner differentiates between the laymen and other than the laymen, and this is a good measure. The laymen [of the Rāfiḍha] who do not slander the wives of the Prophet (ṣallallāhu ʿalayhi wa sallam) who do not make takfīr upon the Companions (raḍiAllāhu ʿanhum) and those who do not believe that the Qurʾān has been distorted, yet they have some elements of rejection [الرفض] within them, and some hatred for the Companions (raḍiAllāhu ʿanhum) without making takfīr of any of them and things similar to that, then those people are considered misguided innovators whom we do not make takfīr upon.

As for the one who joins their infidels [of the Rāfiḍha] by making takfīr of the Companions (raḍiAllāhu ʿanhum), slandering and defaming the wives of the Prophet (ṣallallāhu ʿalayhi wa sallam), holding a filthy belief that the Qurʾān has been distorted, and that parts have been added and removed from it – then this person is a disbeliever just like the Jews, Christians and other than them from the disbelievers. There is no difference between their scholars and their laymen (who hold these beliefs).

Interact with them if it is in relation to worldly affairs such as trading or anything similar to that. It is permissible to interact with the Jews, Christians and a Rāfiḍhī. As for co-operating with them in matters related to the religion, then never! Since [by doing so] you will be co-operating upon sin and transgression.