When is it said that a narrator is of unknown status or that he is not known?

The questioner : My Shaykh, when do they express it by saying he is of unknown status or that he is not known?

The Shaykh : When do they express it by saying he is of unknown status or that he is not known? That comes down to one of two things. The first is that he is preceded by those who have stated, among the scholars of the critique and vindication of narrators, that he is of unknown status, so one relies on them and says this phrase. As for the other phrase, which is "I do not know him," this is something that people like us, the later scholars, can say, for it is difficult for us to determine the status of that narrator about whom the earlier scholars say he is unknown, oh Allah.