Hearing has special importance because much religious learning is transmitted through truthful report, often heard from a speaker. Yet hearing a report is not equivalent to establishing its credibility.
Two speakers may utter competing statements and both may be heard perfectly. Their words reach the ear, but their truthfulness does not thereby become equal. Hearing transmits an utterance; evaluating testimony requires a different epistemic standard.
A written report may be read through sight, but vision by itself does not authenticate its content.
This distinction between the physical channel and the warrant for belief prepares the next discussion of al-khabar al-ṣādiq.