Someone said to Abu Bakr , "Caliph of Allah," but he replied, "I am the successor of the Messenger of Allah ﷺ, and I am content with that, I am content with that, I am content."
حدثنا موسى بن داود حدثنا نافع يعني ابن عمر
قيل لأبي بكر رضي الله عنه يا خليفة الله فقال أنا خليفة رسول الله ﷺ وأنا راض به وأنا راض به وأنا راض
Its chain is daif due to a break in transmission, for Ibn Abu Mulayka, whose name was Abdullah bin Ubaydullah, is a trustworthy tabii, but he did not meet Abu Bakr. Nafi is Ibn Umar bin Abdullah bin Jameel Jumahi Makki, the hadith master, who is trustworthy.