Tracing the athar of al-Hasan al-Basri

The Shaykh: Praise is to Allah; we praise Him, seek His help, and seek His forgiveness. We seek refuge in Allah from the evils of our own selves and from the badness of our deeds. Whomsoever Allah guides, none can misguide, and whomsoever He leaves to misguide, none can guide. And I bear witness that there is no deity but Allah alone, with no partner, and I bear witness that Muhammad is His slave and His Messenger, , , . As for what follows:
Indeed, the best of speech is the speech of Allah, the best of guidance is the guidance of Muhammad (peace and blessings be upon him), and the worst of matters are their innovations. Every innovation is a religious innovation, every religious innovation is misguidance, and every misguidance is in the Fire. And after that:
As for the following, it is hasan (a good hadith), and it is his statement: "It was narrated from him—meaning al-Hasan—that he said: 'They hoped that the heat of the night would be an expiation for the sins that had passed.' Ibn Abi al-Dunya narrated it, and its narrators are trustworthy." This hadith does not explicitly state that it was raised to the Prophet (peace and blessings be upon him), because, first of all, it is from the narration of al-Hasan, who is al-Hasan al-Basri. We have learned from our previous lessons that al-Hasan al-Basri was a man among the most distinguished and great scholars of the Tabi'un (the generation after the Companions), their ascetics, and their brave ones. He possessed many qualities that are rarely found in individuals. However, from the perspective of hadith science, there is something that prevents a hadith scholar from using his hadith as evidence in some cases. This occurs when he narrates a hadith from a Companion, or even from someone below him among the Tabi'un, using the phrase "from" (an), or the phrase "said" (qala), or any other phrase that does not explicitly state that he heard the hadith from that Companion or other person. If he does not explicitly state that he heard it, his hadith is not used as evidence, despite his high status and virtue. This is because he is classified among the mudallis (those who conceal defects in chains) by those who know hadith science and its terminology.