As for error, most people are not free of it. Indeed, some Companions occasionally made mistakes, as did some of those who came after them. Thus, collections of authentic hadith contain some reports known to be erroneous, although the majority of the hadith texts in the two Sahīh collections are known to be true. The hadith master Abū al-‘Alā’ knows that these reports are erroneous. Imam Ahmad himself explained this and stated that he transmitted them so that they could be recognized, unlike reports whose narrators deliberately lied.

For this reason, Ahmad kept his Musnad free of reports from certain narrators whose reports are transmitted by compilers of the Sunan, such as Abū Dāwūd and al-Tirmidhī. An example is the mashyakha of Kathīr ibn ‘Abd Allāh ibn ‘Amr ibn ‘Awf al-Muzanī, transmitted from his father, from his grandfather. Although Abū Dāwūd includes some of these reports in his Sunan, Ahmad’s criteria for his Musnad are better than Abū Dāwūd’s criteria for his Sunan.

The point is that the hadiths transmitted on this subject are like other singular and rejected reports—indeed, fabricated reports—transmitted by those who indiscriminately collect the good and the bad concerning merits and distinctions. Similar material is found in works on the merits of particular times, acts of worship, prophets and Companions, places, and the like. These subjects contain authentic hadiths, sound hadiths, weak hadiths, and fabricated lies.

It is not permissible to rely in matters of the Sharia on weak hadiths that are neither authentic nor sound. However, Ahmad ibn Hanbal and other scholars permitted the transmission, concerning the merits of deeds, of reports not known to be established, provided they are not known to be lies.