Abu Idris al-Khawalani said,
“I entered the mosque of Damascus and there was a young man with shinning (white) teeth sitting with some people. When they disagreed about something. they referred it to him and followed his opinion. I inquired about him and it was said, “That is Mu’adh ibn Jabal”.
The following day, I went early and I found that he had come earlier than me and I found him praying. I waited for him until he finished his prayer and then I approached him from the front. I greeted him and then said, “By Allah, I love you for Allah.” He said, “By Allah?” and I said, “By Allah.” He said, “By Allah?” and I said, “By Allah.”
He took hold of the upper part of my cloak and pulled me to him.
He said, “Rejoice! I heard the Messenger of Allah (saw) say, ‘Allah Almighty says, ‘My Love is mandatory for those who love one another in Me and sit together for My Sake and who visit one another for My Sake and who give generously to one another for My Sake.’
(Malik transmitted this in al-Muwatta, quoted in “Tahdhib al-Akhlaaq” page 92)