Sunan At-Tirmidhi

Narrated Anas bin Malik:""The Prophet (ﷺ) sent Abu Bakr with the (announcement of) Bara'ah (the declaration to publicize the disavowal of the idolaters). Then he summoned him and said: 'It is not right for anyone to convey this except a man among my family.'""So he called for 'Ali and gave it to him