Sunan an Nasai
1561
Sahih Isnaad+2

It was narrated from Tha'labah bin Zahdam that:'Ali appointed Abu Mas'ud over the people, then went out on the day of 'Eid and said: 'O people, it is not part of the sunnah to pray before the imam

Sahih IsnaadAbu Ghuddah
Sahih IsnaadAl-Albani