THE RUWAT...
THE RUWAT: Some important qualifications of a RAWI are as follows: The RAWI of a HADITH must be an adult (BALIGH), sane, Muslim, just (ADIL), and of good memory; according to the SHI'A ITHNA ASHERI sect, he should also be a SHI'A ITHNA ASHERI, though in some cases, the AHADITH narrated by non-ITHNA ASHERI Muslims are acceptable. ADIL means a person who does not commit any major sin (not intentionally) then he repents at once. Only an ADIL person can be relied upon.
If he is not ADIL, he might forge AHADITH and mislead people. Good memory is necessary for a RAWI if he is to be trusted; otherwise, he may forget something and thus change, add or omit some wordings from the HADITH. It is not necessary that a RAWI should be a scholar or learned person.
The Four Types Of Hadith ALLAMAH AL-HILLI and the ULAMA coming after him have divided the AHADITH into four categories according to the qualifications of the RUWAT: SAHIH (Correct: True): A HADITH all of whose RUWAT are SHI'A ITHNA ASHERIS and all have been praised for their trustworthiness. For example, such wordings have been used for all of them: "He is trustworthy- THIQAH": "His AHADITH are correct- SAHIHU'L- HADITH" and such other words which show their trustworthiness.
HASAN (Good): A HADITH, all of whose narrators are SHI'A ITHNA ASHERIS but not all of them have been praised for trustworthiness; instead some or all have been praised in such word: "He is virtuous -MUSTAHSAN" or "He is of good memory- HAFIDH". MUWATHTHAQ (Reliable): A HADITH not all of whose narrators are SHI'A ITHNA ASHERI, but all have been praised for trustworthiness. DA'IF (Weak): A HADITH, which is neither SAHIH, HASAN nor MUWATHTHAQ. The first three categories are considered as genuine.
DA'IF has got no worth at all, unless it was accepted by all 'ULAMA of the early period, in which case it is called MAQBUL (acceptable), that is, accepted by early scholars. As has been mentioned earlier, a HADITH consists of a SANAD (chain of narrators) and a MATN (text). If a HADITH is classified as DA'IF (weak), it means that that particular SANAD is weak.
But that same text might have been narrated somewhere else with SAHIH, HASAN or MUWATHTHAQ SANAD; and the value of HADITH will change accordingly.