Al-Adab Al-Mufrad, Hadith 901 ⓘ
Abu Hurayra reported that the Messenger of Allah, may Allah bless him and grant him peace, said, "The spirits are massed armies. Those of them that knew one another are friendly. Those that did not know one another disagree."
حَدَّثَنَا عَبْدُ الْعَزِيزِ بْنُ عَبْدِ اللهِ قَالَ: حَدَّثَنِي سُلَيْمَانُ بْنُ بِلاَلٍ، عَنْ سُهَيْلٍ، عَنْ أَبِيهِ، عَنْ أَبِي هُرَيْرَةَ قَالَ: قَالَ رَسُولُ اللهِ صلى الله عليه وسلم: الأرْوَاحُ جُنُودٌ مُجَنَّدَةٌ، فَمَا تَعَارَفَ مِنْهَا ائْتَلَفَ، وَمَا تَنَاكَرَ مِنْهَا اخْتَلَفَ.
also referenced under: Book 38, Hadith 14 (In-Book) & Book 38, Hadith 901 (English)