Quran 24:28

فَإِن لَّمۡ تَجِدُواْ فِيهَآ أَحَدً۬ا فَلَا تَدۡخُلُوهَا حَتَّىٰ يُؤۡذَنَ لَكُمۡ‌ۖ وَإِن قِيلَ لَكُمُ ٱرۡجِعُواْ فَٱرۡجِعُواْ‌ۖ هُوَ أَزۡكَىٰ لَكُمۡ‌ۚ وَٱللَّهُ بِمَا تَعۡمَلُونَ عَلِيمٌ۬ ٢٨

If you find no one in them, do not enter them until you obtain permission. If you are told, "Go back," you must go back. This is purer for you. ALLAH is fully aware of everything you do.