The third is narrating from memory, for not everyone can do this accurately.

The fourth is that someone inserts into his narrations material that does not belong to them and falsely attributes it to him.

The fifth is relying on students and consequently narrating what he supposes to be among his own reports.

The sixth is transmitting with an incomplete chain, for the omitted narrator may not be acceptable.

The seventh is narrating from a written text, because discrepancies may occur in it. For these and other reasons, a narrator is required to possess sound retention and accuracy, together with the qualities that safeguard against his conveying falsehood unwittingly. A narrator may have been free of lapses, yet subsequently lapse in another of his reports. Glory be to Him who neither errs nor forgets! Specialists in this discipline recognize such errors by comparing the narrations of his counterparts and contemporaries. An inattentive narrator’s report may nevertheless be accompanied by evidence establishing its accuracy, such as indications showing that he retained what he narrated and that not everything he transmitted was confused.

Deliberate lying has several causes:

The first is heresy and deviation in Allah’s religion:

“But Allah refuses to do anything but perfect His light, however much the disbelievers may detest it.”

The second is championing schools of thought and sectarian inclinations. This is common in fundamental matters, subsidiary matters, and those in between.