An Imam of a Masjid (mosque) seeks help from dead people in their graves, claiming that these are the graves of Awliya’ (pious people) to whom we should resort. He says that they may act as mediators between us and Allah (Exalted be He). Am I allowed to perform congregational Salah (Prayer) behind this Imam, despite the fact that I call for Tawhid (belief in the Oneness of Allah)?
Could you please also clarify such questions as making vows, seeking help from other than Allah, and Tawassul (seeking to draw close to Allah) through a means.
(Part No. 1; Page No. 119
If you are sure that the Imam you mentioned seeks help from the dead or vows to them, then it is not permissible to perform Salah behind him because he is considered a Mushrik (one who associates others with Allah in His Divinity or worship); the Salah he performs individually as well as the congregational Salah that he leads are Batil (null and void). Furthermore, it is not permissible for a Muslim to perform Salah behind him, as Allah (Glorified be He) says (what means):
But if they had joined in worship others with Allâh, all that they used to do would have been of no benefit to them.
And indeed it has been revealed to you (O Muhammad صلى الله عليه وسلم), as it was to those (Allâh’s Messengers) before you: "If you join others in worship with Allâh, (then) surely (all) your deeds will be in vain, and you will certainly be among the losers."
Nay! But worship Allâh (Alone and none else), and be among the grateful.
May Allah grant us success. May peace and blessings be upon our Prophet Muhammad, his family, and Companions.