Sayyiduna ‘Umar (RA) is reported to have said:
وَلَا تَدْخُلُوا عَلَى الْمُشْرِكِينَ فِي كَنَائِسِهِمْ يَوْمَ عِيدِهِمْ فَإِنَّ السَّخْطَةَ تَنْزِلُ عَلَيْهِمْ
“Do not enter the places of worship of the polytheists on the day of their festival, for divine wrath descends upon them at that time.”
It is both desirable and just for the state administration—and, where necessary, political leaders as well—to safeguard the religious rights of non-Muslim citizens, provide administrative assistance to ensure that their festivals and ceremonies are conducted safely and without hindrance, and take the necessary measures to that end.
However, it is in no way appropriate for a believer to visit the worship pavilions of other religious communities and deliver greetings or congratulatory speeches at those venues.
This is, on the one hand, wholly contrary to the spirit of faith; on the other, it amounts to encouraging their polytheistic practices.
Administrative or political leaders who wish to extend greetings out of human courtesy, goodwill, civic harmony, and peaceful coexistence—particularly in a multi-ethnic society—would be well advised to prepare their speech scripts in advance and with due care.
This would help ensure that their remarks contain no inappropriate words or expressions that, whether through ignorance or unintentionally, could be construed as endorsing disbelief or polytheism. It would also help prevent misunderstandings within their own communities and avoid situations in which they later have to offer explanations to clarify what they meant.