Abu al-Bakhtari said, or perhaps Amir narrated it, that Sayyiduna Ibn Mas'ud (may Allah be pleased with him) entered the mosque and saw two circles. He said to the boy: Go and see whether these people sat first or those. He went, came back and said: These people sat first. So he said: "One speaker is enough for the mosque; those before you were destroyed only through rivalry with one another."
Hadith Referenceالمعجم الكبير للطبراني / باب العين / 8599