Abu Bakr belonged to a tribe of slaves and maids

Tarikh Tabari, vol. 3, p. 531 narrates that,

Umair Ibn Al-Ahlab al-Dhabbi was with Ayesha in the Battle of Jamal but regretted when he was injured and about to die. When somebody came to ask him about his well-being, he told him to come near him.

When that person came near, he bit his ear! Shocked, that person asked the reason for his stupid act.

He replied that when anybody asks you how this happened, say the following poem to him:

…
نصرنا بني تيم بن مرة شقوة و هل تيم إلا أعبد و إماء
We helped the Tribe of Taym bin Murrah on account of our wretchedness
And are the tribe of Taym anything except slaves and maids

The last verse shows that Banu Taym was the tribe of slaves and slave-girls (al-Fusul al-Mukhtaarah, p. 87)