As for the four conditions of narration, they are as follows:
The first condition is Islam:
There is no disagreement that the narration of a disbeliever is not accepted because he is accused in regard to religion even if the testimony of some of them over others are accepted according to Abu Hanifah (may Allah be pleased with him) otherwise there is no disagreement in rejecting their narrations.
The second condition is reaching puberty age:
So, the narration of a child is not accepted because there is no deter for him not to tell lies, so trust is not attained by his saying. The saying of a debauchee is more accurate than the saying of an adolescent and it is known that the narration of a debauchee is rejected, so how would be the case with an adolescent?
Another reason which is: His confession in regard to himself is not accepted, so how will it be accepted in regard to others?!
In case he was a child upon hearing the Hadith then he grew up and delivered the narration, his narration shall be accepted because the defect was removed.
The proof to the permissibility of accepting the narration of an adolescent is the consensus of the Companions (may Allah be pleased with them) who accepted the narrations of young adolescents such as Ibn`Abbas, Ibn Az-Zubayr, Abu At-Tufayl, Mahmoud ibn Ar-Rabi` and others without any difference between the narrations they heard before puberty age or after.
The Pious Predecessors used to take their children to the sessions of Hadith and accepted the narrations they heard before puberty age.
However, the scholars of Hadith put a terminology for adolescents to indicate whether they reached puberty age or not. So, they used to add the word "attendance" when they did not reach the puberty age, but when they reach the puberty age, they used to write "by listening;" that was very common to the extent that they used to write the word "attendance" for very young children.
The third condition is accuracy:
It is a cautionary procedure in this knowledge which has two sides:
The side of gaining knowledge at listening and the side of memorizing the Hadith after knowledge. So, if a person listened to a Hadith and did not know its meaning or if he had heard something that has no meaning such as he heard yelling or if he does not understand the word as should, all these cases are not part of accuracy. Moreover, if he had some doubts about the narration after gaining knowledge and after listening, he is not accurate.
Accuracy is of two types: Apparent and hidden.
The apparent means: Accuracy of the meaning from linguistic aspect.
The hidden means: Accuracy of the meaning from juristic aspect which is called Fiqh.
The general meaning of accuracy is the apparent meaning of accuracy because it is permissible to convey the narration by meaning as shall be explained later, then he will be accused of changing the meaning by narrating it before memorization or before gaining knowledge just by listening. Therefore, the transmission of narrations at the time of the Companions (may Allah be pleased with them) were few because of that reason. So, whoever was underage at listening to the Hadith or was fool who does not how to master what he has memorized to convey it properly, his saying shall not be trusted even if he is not a debauchee.
However, the scholars of Hadith rarely consider this condition in regard to children not fools because when a child listens to a Hadith or attends the session of reading Hadiths, they permit his narration; however the first view is more preventive for the religion.
It is worth mentioning that accuracy in our time is rare because the highest degrees of a narrator in our time is to narrate Hadiths or sit in a session to make the people listen to Hadiths.
As for the means of transmitting a Hadith, a narrator would have a copy which he read or heard or he would have a copy in his country in which his name is written or he was given a permission to transmit this Hadith. So, when someone reads a Hadith, the scholar listens then writes for him with his own handwriting that so and so has read that to him and he listened to his reading. Sometimes, a reader changes some letters which his Sheikh did not know or found, and when the Sheikh asks his student about them, he would answer: I heard them as such.
When you contemplate the conditions of the scholars of Hadith in our time, you will find them as we mentioned. They do not have much knowledge about the correct or false narrations, but they only know the general information that we mentioned. Nevertheless, in every time and place you find real scholars whom people follow, memorizers form whom people take narrations, scholars whom are followed by people, and virtuous people who guard this knowledge of being lost and recite it correctly as they heard, protect it against distortion, and guard it from errors and confusion.
May Allah make you and us benefit from those scholars, and may Allah guide you and us to the best saying and action.
The fourth condition is: Trustworthiness
Trustworthiness means integrity of reputation and religion. Its core is something in oneself that pushes a person to adhere to piety and magnanimity until people trust his truthfulness. It is not a condition that such a person should be free of all sins, and it is not enough that he should avoid major sins because minor sins may make testimony and narration rejected.
In general, anything that indicates the softness of one's religion to the extent that he may attribute lies to Allah in order to gain worldly benefits is against trustworthiness. How could such attributes accepted in a person while avoidance of some permissible matters is conditioned in trustworthiness such as eating and drinking in public roads, urinating in streets, and so on?!
Some people said: Trustworthiness is showing Islam along with avoidance of apparent lewdness, so according to this view, any Muslim is trustworthy as long as his conditions are not known.
Trustworthiness is known by experiencing a person and searching about his conditions and reputation.
Some people of Hadith accepted narrations from the Kharijites, Qadariyyah, Shi`ites, and people of heresies and those who follow whims, whereas others refused to accept their narrations, and they all are exerting efforts in verification. May Allah guide all scholars to seek the truth and act accordingly.
These four conditions are considered in accepting narrations as we mentioned.
Narrators also have attributes which some people consider as conditions where they are not, but they are complementary and improvement.
Of which is the knowledge and Fiqh:
It is not a condition that a narrator would be a scholar or Faqih (jurist) whether he disagrees with Qiyas (analogy) or not because a person may convey knowledge to someone who can understand it better. Some people considered this a condition, but it is a weak view.
Of which is accompanying scholars and listening to Hadiths:
This is not a condition because the Companions (may Allah be pleased with them) accepted the narration of a bedouin who did not narrate but a single Hadith. This condition can be considered if the narration of an ordinary man was contradicted by the narration of a scholar, then probability may take place.
Of which also is the knowledge of a narrator’s lineage:
This is not a condition but when the trustworthiness of a narrator is ascertained, his narration will be accepted without knowing his lineage. If a narrator reported a narration from unknown person, it will not be accepted because the unknown person may be a debauchee.
In case a narrator reported from a person whose name is listed in both criticized and trustworthy narrators, his narration shall not be accepted because of that hesitation. However, the scholars of Hadith reported narrations from unknown narrators then their followers accepted these Hadiths by transmitting them from different chains of transmissions then the unknown narrator has become known by these different narrations, so it is as if they did not report from unknown narrators. Or perhaps they knew him but did not mention his name for some reason, and Allah knows the best!
The narration of a person who is known for playing, joking, and jesting is not accepted or a narrator who does not have strict conditions for accepting narrations or a narrator who forgets a lot because all these narrators are not trustworthy.
Of the things needed by a student of Hadith to know is to search for the conditions of his Sheikh from whom he takes knowledge after he ascertains his sound faith, correct doctrine, and makes sure that he is not a whim follower or innovator in religion who invites people to add or omit something in religion.
When Ali ibn Abu Talib (may Allah be pleased with him) missed a Hadith then he heard it from another, he would make the narrator swear that the narration is true.
Likewise did most Companions, Followers, and Successors (may Allah bestow mercy on them all) whom should be followed.