Surah An-Nur — Ayah 28 (24:28)
فَإِن لَّمۡ تَجِدُواْ فِيهَآ أَحَدٗا فَلَا تَدۡخُلُوهَا حَتَّىٰ يُؤۡذَنَ لَكُمۡۖ وَإِن قِيلَ لَكُمُ ٱرۡجِعُواْ فَٱرۡجِعُواْۖ هُوَ أَزۡكَىٰ لَكُمۡۚ وَٱللَّهُ بِمَا تَعۡمَلُونَ عَلِيمٞ ٢٨
English translation (Saheeh International)
And if you do not find anyone therein, do not enter them until permission has been given you. And if it is said to you, "Go back,"1 then go back; it is purer for you. And Allāh is Knowing of what you do.
- - Or a similar expression showing that the occupants are not prepared to receive visitors (which should be respected).
Brief commentary
But if you do not find anyone in those houses, do not enter them until you are permitted to enter by those who have the authority to give permission. And if their owners tell you to return, return and do not enter them, as this is purer for you in the sight of Allah. Allah is Knowing of what you do; none of your actions are hidden from Him and He shall reward you for them.