Al-Harith bin Amirah said: When I arrived in al-Mada'in, I set off walking, and suddenly my eyes fell on a man wearing worn-out clothes, with a piece of red leather which he was kneading. I turned (towards him), and he looked at me and gestured with his hand: Stay where you are, O servant of Allah. I stood still and asked the people who were with me: Who is this man? They said: This is Sayyiduna Salman (may Allah be pleased with him). Then he went into his house and put on white clothes, then came, took my hand, shook hands with me and asked how I was. I said: O Abu Abdullah! You have never seen me before, nor have I seen you, nor do you know me. Sayyiduna Salman al-Farisi (may Allah be pleased with him) said: Indeed I do. By the One in whose hand is my soul, when I saw you my soul recognised your soul. Are you not al-Harith bin Amirah? I said: Indeed I am. He said: I heard the Messenger of Allah (peace and blessings be upon him) say: "Souls are like assembled troops: those that recognise one another for the sake of Allah become intimate, and those that do not recognise one another for the sake of Allah differ."
Hadith Referenceالمعجم الكبير للطبراني / باب السين / 6147