An-Nur - 24:28

فَإِن لَّمْ تَجِدُوا فِيهَا أَحَدًا فَلَا تَدْخُلُوهَا حَتَّى يُؤْذَنَ لَكُمْ وَإِن قِيلَ لَكُمُ ارْجِعُوا فَارْجِعُوا هُوَ أَزْكَى لَكُمْ وَاللَّهُ بِمَا تَعْمَلُونَ عَلِيمٌ
[24:28]
But if you do not find any one therein, then do not enter them until permission is given to you; and if it is said to you: Go back, then go back; this is purer for you; and Allah is Cognizant of what you do.
If ye find no one in the house, enter not until permission is given to you: if ye are asked to go back, go back: that makes for greater purity for yourselves: and Allah knows well all that ye do.
And if ye find no-one therein, still enter not until permission hath been given. And if it be said unto you: Go away again, then go away, for it is purer for you. Allah knoweth what ye do.