Banu Sa'ida (Arabic: بنو ساعدة, Banu Sā'idah; Hebrew: בני סאעדה) was one of the Jewish tribes of Arabia during Muhammad's era.
They were included in point 31 of the Constitution of Medinah as being peaceful with the Muslims, being as "one nation", but retaining their Jewish religion.
It was in their Saqifah that Abu Bakr was elected as the first Caliph of Sunnis.
References
Banu Sa'ida Wikipedia(Text) CC BY-SA