Ibn As-Salaah states that although one must state the reasons for Jarh (discrediting an individual) , if this is not done, it still creates a doubt as to the persons reliability. Al-‘Iraaqee commented on this stance by Ibn As-Salaah by stating:
“The majority of the scholars only mandated a clarification when criticizing from those who were now knowledgeable of the causes of jarh (discrediting a narrator) and Ta’deel (validation/praising a narrator). But as for the one who was aware of their causes, then they would accept his jarh (discrediting of a narrator) without (him having to offer) any explanation (for it).
This becomes clearer in what Al-Khateeb quoted in Al-Kifaayah from Al-Qaadee Aboo Bakr Al-Baaqilaanee that he related that the view of the majority of the scholars was:
‘When a jarh (discrediting) comes from a person who does not know jarh, it is an obligation to explain it.’
But this is not required for those who possess knowledge of this field. Al-Qaadee said:
‘The strongest view in our opinion is that no explanation is needed when the critic is knowledgeable (about jarh), just as it is not required for a person grading someone reliable not to explain those statements by which a praised individual becomes trustworthy…’
What we have quoted here from Al-Qaadee Aboo Bakr is the most correct view.”
[Muqaddamah Ibn As-Salaah Ma’a At-Taqyeedi Wal-Eedaah, p.141]