Well,
I came across a few information which could provide you the answer what you are looking for,
Al-Shafi`i states the following requirement in order for a hadith which is not Mutawatir to be acceptable:
"Each reporter should be trustworthy in his religion; he should be
known to be truthful in his narrating, to understand what he narrates,
to know how a different expression can alter the meaning, and report
the wording of the hadith verbatim, not only its meaning. This is
because if he does not know how a different expression can change the
whole meaning, he will not know if he has changed what is lawful into
what is prohibited. Hence, if he reports the hadith according to its
wording, no change of meaning will be found at all. Moreover, he
should be a good memoriser if he happens to report from his memory, or
a good preserver of his writings if he happens to report from them. He
should agree with the narrations of the huffaz (leading authorities in
hadith), if he reports something which they do also. He should not be
a Mudallis, who narrates from someone he met something he did not
hear, nor should he report from the Prophet (may Allah bless him and
grant him peace) contrary to what reliable sources have reported from
him. In addition, the one who is above him (in the isnad) should be of
the same quality, [and so on,] until the hadith goes back
uninterrupted to the Prophet (may Allah bless him and grant him peace)
or any authority below him."
-al-Shafi'i, p. 370f (Eng. trans., pp. 239- 240).
Ibn al-Salah, however, defines a Sahih hadith more precisely by saying:
"A Sahih hadith is the one which has a continuous isnad, made up of
reporters of trustworthy memory from similar authorities, and which is
found to be free from any irregularities (i.e. in the text) or defects
(i.e. in the isnad)."
