Al-Adab Al-Mufrad, Book 42, Hadith 1010 (English) ⓘ
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."
حَدَّثَنَا عَبْدُ اللهِ بْنُ صَالِحٍ قَالَ: حَدَّثَنِي مُعَاوِيَةُ، عَنْ أَبِي مَرْيَمَ، عَنْ أَبِي هُرَيْرَةَ، أَنَّهُ سَمِعَهُ يَقُولُ: مَنْ لَقِيَ أَخَاهُ فَلْيُسَلِّمْ عَلَيْهِ، فَإِنْ حَالَتْ بَيْنَهُمَا شَجَرَةٌ أَوْ حَائِطٌ، ثُمَّ لَقِيَهُ فَلْيُسَلِّمْ عَلَيْهِ.
also referenced under: Hadith 1010 (Reference) & Book 42, Hadith 47 (In-Book)