We have some masajid in Britain that bring a person who is upon the methodology of the Sunnah, in order that he may teach or lecture people about Tawḥīd. Then on following day, they will bring a Ṣūfī or Ashʿarī who will teach the people Ṣūfī or Ashʿarī [ʿaqīdah]. Is it permissible for this Sunni preacher to teach in such a masjid?

Shaykh Ṣāliḥ al-Fawzān:

No, If they [the masājid] mix between him [the Sunni] and an innovator or a deviant, it is not permissible for him [to teach there]. This is because, they are using him as a disguise. They say [to the people], ‘We teach Tawḥīd and we listen to lectures in Tawḥīd!’ This is not correct, since this is mixing the truth and falsehood.   [The Sunni] should place a condition on them and say, ‘I will teach or deliver lectures for you on a condition that you do not bring individuals whom are in opposition to that which I say [teach] to you and call you to.