Kalda ibn Hanbal reported that Safwan ibn Umayya sent him to the Prophet, may Allah bless him and grant him peace, during the Conquest of Makka with some milk, gazelle, and cucumber. (Abu 'Asim said that the meant vegetables.) The Prophet, may Allah bless him and grant him peace, was at the top of the valley and I did not give the greeting nor ask for permission. He said, "Go back and say, 'Peace be upon you. May I enter?' That was after Safwan had become Muslim."  

أَخْبَرَهُ أَنَّ صَفْوَانَ بْنَ أُمَيَّةَ بَعَثَهُ إِلَى النَّبِيِّ ﷺ فِي الْفَتْحِ بِلَبَنٍ وَجِدَايَةٍ وَضَغَابِيسَ قَالَ أَبُو عَاصِمٍ يَعْنِي الْبَقْلَ وَالنَّبِيُّ ﷺ بِأَعْلَى الْوَادِي وَلَمْ أُسَلِّمْ وَلَمْ أَسْتَأْذِنْ فَقَالَ ارْجِعْ فَقُلِ السَّلاَمُ عَلَيْكُمْ أَأَدْخُلُ؟ وَذَلِكَ بَعْدَ مَا أَسْلَمَ صَفْوَانُ  

Abu Hurayra reported that the Messenger of Allah, may Allah bless him and grant him peace, said, "If someone looks inside, he should not be given permission to enter."  

أَنَّ رَسُولَ اللهِ ﷺ قَالَ إِذَا أَدْخَلَ الْبَصَرَ فَلاَ إِذْنَ لَهُ