لَا عِبْرَةَ بِالظَّنِّ فِي بَابِ الِاعْتِقَادِيَّاتِ
Mere conjecture cannot be treated as certainty in matters of creed.
Establishment of a report and what it signifies are separate questions. The fact that a report has a particular chain does not dispense with examining its meaning and certainty. A decisive numerical claim about the prophets requires decisively supporting evidence.
This distinction does not nullify every practical use of solitary reports. The narrower point is that a debatable probabilistic narration should not automatically be elevated to an obligatory, indisputable element of doctrine.