Is it permissible to join Islamic da'wah groups and Islamic movements?

Working collectively is permissible and desirable if it is based on truth and cooperation, but on condition that it does not turn into partisanship or fanaticism that rejects the truth or justifies falsehood. If the group adopts the methodology of the Ahl al-Sunnah (definition) wal-Jama’ah (People of the Sunnah and the Community), then cooperation with it and supporting it is permissible. It must be known that truth is not known by men, and that obedience to any person is restricted by obedience to Allah and His Messenger. A Muslim must accept the truth from any source and clarify that his loyalty to the truth does not mean his hatred or disassociation from those outside his group. As for loyalty to a slogan or a person, that is an act of the people of innovation, and allegiance (bay’ah) is given to the general Imam whom the people gather around. These groups may be means of da’wah (invitation to Islam), but Islam is the arbiter over them and is not confined within them.