Imam Mansur Al-Buhuti (d. 1051 AH (AD 1656), may Allah be pleased with him, said: “Whoever believes that there is another way to Allah other than by following His Religion or following the Prophet Muhammad, peace and blessings of Allah be upon him, or that he may follow another way besides or that he is not required to is certainly an unbeliever.”
He went on to say, “And whoever believes that the synagogues and churches are the Houses of Allah, that Allah is worshiped therein and that what the Jews and Christians do inside is worship and obedience to Him and to His Messenger and that He loves that or He is pleased with that is indeed an unbeliever on account of his believing in the validity of their Religion and this is kufr as we have discussed. Furthermore, whoever assisted them in opening synagogues and churches, establishing their religion while believing that doing so is nearness to Allah and obedience is certainly an unbeliever as he is affirming the validity of their Religion.
“Taqi ud-Din Ibn Taymiyyah mentioned in one place that whoever believed that visiting the Jews and Christians under covenant to the Muslims in their synagogues and churches or places or worship is nearness to Allah is indeed an apostate. If he is ignorant of that fact, then he is made to know the reality. If he should persist in such an act after knowing this, then he is indeed an apostate.” Please see Kash-shaf ul-Qina an Matn il-Iqna, vol.5, pp. 145-147 for all of the above and more.
In all such cases, in a land in Dar ul-Islam, you have to ask: (1) WHY are there gurdwaras in open operation and (2) WHY are the Muslims eating iftar in a gurdwara when this is Dar ul-Islam. Sure, in somewhere like India/Pakistan where Islam is a persecuted minority or weak to the point of their not being able to implement the Religion (or nearly extinct), this could be a concession if starvation was certain.
But in Dar ul-Islam? In a place where Islam is not only dominant but the only reality preached for the public?
This should show us that even in this month of Ramadan, we still have to be mindful of the kufr of universalism and religious indifferentism. Both are still kufr and we are still Muslims. Let us beware and remember that the month of Ramadan is not for remembering the poor, it is the celebration of the Revelation of the Qur’an.