Sayyiduna Abdullah bin Abbas (may Allah be pleased with them both) narrates: The Prophet (peace and blessings be upon him) said: "Whoever hears the sound of a naqus (church bell), or enters a place of worship of the Jews or the Christians, or enters a fire temple or a temple of idols, and recites:
'La ilaha illallah, wa la na'budu illa iyyah' (There is no god but Allah Almighty, and we worship none but Him),
(The Prophet (peace and blessings be upon him) said:) then Allah Almighty grants that person reward equal to the number of those who did not recite it (i.e. the kalimah); (here the narrator is perhaps in doubt, and the words may be:) that person is recorded with Allah Almighty as a 'siddiq' (truthful one)."
Tabarani recorded it; its chain contains a narrator, Umar bin al-Subh, who is matruk (abandoned).
Hadith Referenceمجمع الزوائد ومنبع الفوائد / كتاب الأذكار / 17157
Hadith Gradingمحدثین:إسنادہ ضعیف جداً
Hadith Takhrij«اخرجه الطبراني فى المعجم الكبير (12691) ، أخرجه المعجم الكبير للطبراني برقم: 12691»