Is a narrator considered trustworthy if the Imam stipulated that he would not narrate except from a trustworthy source?

The questioner : ... Is it considered a validation if he stipulated that he would not narrate except from a trustworthy source?

The Shaykh : If the condition is found, the conditioned thing is found; otherwise, it is not.

The questioner : Know that Imam Ahmad, for example, was described as one who does not narrate except from a trustworthy source, and yet Ibn Ma'in says of him: "Ahmad has gone mad; he narrates from 'Amir ibn Salih." Likewise, Shu'bah was found to have narrations from weak narrators in his transmission, and so on. Perhaps this condition was adopted later in the narrator's life...

The Shaykh : As we said earlier, if the condition is found, the conditioned thing is found, but on the condition that the one being validated by this method is not criticized by some of the scholars of al-jarh wa al-ta'dil (the critique and vindication of narrators). If he is free from this, then the validation is sound, effective, and clear in this state, when he cites what is most likely not an error.
The student : Muhammad in it...

The Shaykh : If this were before that, if it were to be obeyed, it would be a short opinion.