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, sallallaahu ‘alayhi wa sallam, is His Slave and Messenger.
We have previously explained the meaning of the Mawqoof Hadeeth in Fatwa 12239.
As for taking it as evidence, it means that we have to act according to it and consider it a source of evidence of the Islamic religion. Scholars have ten different opinions regarding that issue. The nearest of them to correctness is that if the opinion of the companion spread widely and no one went against it, then it is a source of evidence and a consensus by silence. However, if it did not spread or some other companions went against it, then it is not a source of evidence, but can be used as secondary evidence.
That is the case if reason and Ijtihaad (personal diligence) can be applied in the opinion of the companion; otherwise (i.e. if his opinion is something that has nothing to do with Ijtihaad like matters of the unseen or the stories of the previous Prophets), then it is regarded as Marfoo‘ (traceable) to the Prophet, sallallaahu ‘alayhi wa sallam, unless it is known that that companion used to take his information from the books of the People of the Book.
Allaah Knows best.