Mu'awiya ibn Qurra said, "My father told me, 'If you sit in a gathering expecting good to come from, but then something occurs which makes you leave, say, 'Peace be upon you,' and you will share in any good that they obtain in that gathering. There are no people who sit in a gathering and then split up without Allah having been mentioned, but that it is as if they were leaving the corpse of a donkey.'"  

قَالَ لِي أَبِي يَا بُنَيَّ إِنْ كُنْتَ فِي مَجْلِسٍ تَرْجُو خَيْرَهُ فَعَجِلَتْ بِكَ حَاجَةٌ فَقُلْ سَلاَمٌ عَلَيْكُمْ فَإِنَّكَ تَشْرَكُهُمْ فِيمَا أَصَابُوا فِي ذَلِكَ الْمَجْلِسِ وَمَا مِنْ قَوْمٍ يَجْلِسُونَ مَجْلِسًا فَيَتَفَرَّقُونَ عَنْهُ لَمْ يُذْكَرِ اللَّهُ إِلاَّ كَأَنَّمَا تَفَرَّقُوا عَنْ جِيفَةِ حِمَارٍ  

Abu Hurayra said, "Whoever meets his brother should greet him. If a tree or wall comes between them and then he meets him, he should greet him on the other side."  

أَنَّهُ سَمِعَهُ يَقُولُ مَنْ لَقِيَ أَخَاهُ فَلْيُسَلِّمْ عَلَيْهِ فَإِنْ حَالَتْ بَيْنَهُمَا شَجَرَةٌ أَوْ حَائِطٌ ثُمَّ لَقِيَهُ فَلْيُسَلِّمْ عَلَيْهِ  

Anas ibn Malik reported that the Companions of the Prophet, may Allah bless him and grant him peace, used to gather and they would turn towards the tree and a group of them would go to the right and a group to its left. When they met again, they would greet one another.  

أَنَّ أَصْحَابَ النَّبِيِّ ﷺ كَانُوا يَكُونُونَ مُجْتَمِعِينَ فَتَسْتَقْبِلُهُمُ الشَّجَرَةُ فَتَنْطَلِقُ طَائِفَةٌ مِنْهُمْ عَنْ يَمِينِهَا وَطَائِفَةٌ عَنْ شِمَالِهَا فَإِذَا الْتَقَوْا سَلَّمَ بَعْضُهُمْ عَلَى بَعْضٍ