It is narrated from Sayyiduna Abdullah bin Mas'ud (may Allah be pleased with him), or from another Companion, that the Messenger of Allah (peace and blessings be upon him) said: "Souls are like assembled troops; those among them that recognise one another come together in harmony, and those that are strangers to one another fall into discord."
Hadith Referenceالمعجم الكبير للطبراني / باب العين / 10511