O Believers, if an unrighteous person comes to you with information, you should verify it or else you might inflict harm on a people in ignorance and then end up regretting what you have done. (Al Qurãn 49:6)
The believers should be concerned about the negative news that they are bombarded with especially when unrighteous people control all the information that reach us in this part of the World. They should pay attention to this verse before they listen and accept any news.
After the battle of Banu Mustalaq (5 AH/627 CE) in which the Mustalaq tribe was defeated and taken prisoners, all members of the tribe were divided up and given to the Muslims of Madeenah as slaves . The Prophet subsequently married Juwayreeyah, daughter of the former king of the Mustalaq tribe, al-Hãrith ibn AbeeDarãr. The marriage made the Sahãbah ashamed to have the relatives of the Prophet's wife as their servants so they freed the rest of the tribe. When all members of the Mustalaq tribe were freed, the Prophet invited al-Hãrith to accept Islãm which he willingly did. The Prophet then asked him to invite the rest of his tribe to Islãm and to collect Zakãh from those who became Muslim. Al-Hãrith agreed and asked the Prophet to send a messenger to collect the Zakãh at a particular time.
When the time arrived and no messenger came, al-Hãrith feared that the Prophet might have been displeased with him in some way so he consulted his tribesmen and they agreed to send a delegation to the Prophet in order to find out the reason for the delay. In the meantime the Prophet sent al-Waleed ibn 'Uqbah to collect the Zakãh from al-Hãrith. However, on the way al-Waleed heard that a group from Banu Mustalaq had set out and he became afraid. He returned swiftly to the Prophet and told him that al-Hãrith had refused to turn over the Zakãh and had threatened his life.
The Prophet became angry and dispatched a group of companions to deal with al-Hãrith. The two groups met and returned to the Prophet, who questioned al-Hãrith as follows; "Why did you refuse to pay the Zakãh and try to kill my messenger?" Al-Hãrith replied, "By the one Who sent you with the truth, I did not see him nor did he come to me, and the only reason I came was because I feared that your reason for not contacting me was due to Allãh's displeasure with us. " Then the verse, O Believers, if an unrighteous person comes to you with news, you should verify it... was revealed.
This verse was revealed confirming the truth of al-Hãrith's statement, reprimanding the Prophet his snap judgement and warning the Believers in general to thoroughly check out any information coming from questionable sources. The principle was designed to avoid judgements which could bring harm to others since our sorrow and regret no matter how great it may be cannot wipe out the hurt caused by false ãcusations though it might have been unintentional. Thus, great caution must always be taken when dealing with information conveyed by people of doubtful character, those whose honesty has not yet been proven or by known sinners.
It should be noted that based on this verse, Islãmic scholars have unanimously ruled that the testimony of one who is known to be unrighteous should be rejected as evidence in court unless verified. (If his testimony can be confirmed, it is obligatory to do so and if it can not be confirmed, it should be flatly rejected). The converse also holds true. The testimony of a just and righteous person does not require verification except in special cases identified by the Ourãn or the Sunnah.
On the basis of the above mentioned legal ruling, the scholars of Hadeeth decided to reject any Hadeeth which had in its chain of narrators an individual classified as Majhool al-Hãl, that is, one whose name is known but his character is unknown, for any such narrator ,night be of bad moral character and his statement false. This shows the great care taken by Hadeeth scholars in weeding out all the questionable narrations thereby preserving the Sunnah in its pristine puruty for later generations.