When Abu Bakr became Calipah, Abu Sufyan came to Imam Ali and inquired why in his presence the caliphate is being assigned to a junior tribe. He requested Imam Ali to extend his hand for taking allegiance, and if people opposed him, he would post a huge contingent of soldiers and horsemen in Madinah for his support. Imam Ali replied " Abu Sufyan, you are always in pursuit of inflicting harm to Islam. I do not your require counsel and admonition. We have selected Abu Bakr as calipah finding him most competent.
(Tabari vol. 3, p 202)