What is the meaning of ‘agreed upon’, when referring to a Prophetic narration? Does it have to be narrated by one single companion, and does its wording and its meaning have to correspond?

All perfect praise be to Allaah, The Lord of the Worlds. I testify that there is none worthy of worship except Allaah, and that Muhammad is His slave and Messenger. We ask Allaah to exalt his mention as well as that of his family and all his companions.

A narration which is "agreed upon" is a narration reported by Imaams Al-Bukhari and Muslim. As-Sayooti said: 'If the scholars say ‘an authentic narration agreed upon’, they mean reported by Imaams Al-Bukhari and Muslim. A narration which is agreed upon may be narrated by one companion only, or by two companions, or by a group of companions. But the expression ‘agreed upon’ does not mean that the narrators agreed in its wording and meaning, as the same narration could be reported by different wordings.'

To conclude, the narration which is agreed upon is a narration reported by Imaams Al-Bukhari and Muslim and which is reported in their books, whether they agreed in its wording or differed in its wording, what is important is that the meaning is the same. 

Allaah Knows best.