Abdullah bin Abbas reported,

Abu Bakr came out while Umar was addressing the people. Abu Bakr said to him, "Sit down."Umar refused.He said again, "Sit down."Umar still refused.So Abu Bakr gave the testimony of faith, and the people turned toward him and left Umar. He said, "To proceed, whoever among you used to worship Muhammad ﷺ, Muhammad ﷺ has died. And whoever used to worship Allah, Allah is Living and does not die. Allah the Exalted has said, 'Muhammad is no more than a messenger' up to 'the grateful' [Aal Imran 3:144]."By Allah, it was as if the people had not known that Allah had revealed this verse until Abu Bakr recited it. The people received it from him, and not a single person heard it without reciting it.

عن ابن عباس قال

إن أبا بكر خرج وعمر يكلم الناس، فقال: اجلس، فأبى، فقال: اجلس، فأبى، فتشهد أبو بكر، فمال إليه الناس وتركوا عمر، فقال: أما بعد، فمن كان منكم يعبد محمدا ﷺ فإن محمدا ﷺ قد مات، ومن كان يعبد الله فإن الله حي لا يموت، قال الله تعالى: {وما محمد إلا رسول} إلى {الشاكرين} [آل عمران: ١٤٤] والله لكأن الناس لم يكونوا يعلمون أن الله أنزلها حتى تلاها أبو بكر رضي الله عنه، فتلقاها منه الناس، فما يسمع بشر إلا يتلوها.