I had a dispute with a friend over his claim that most Hadeeths are inauthentic since the narrators were not contemporaries of the Prophet, sallallaahu ‘alayhi wa sallam (may Allaah exalt his mention). He also alleges that Jihaad is the sixth pillar of Islam, because the Quran speaks about it more than any other thing.
In addition, he believes that the emergence of different Islamic groups and the disagreements among scholars prove that almost all Hadeeths are distorted.
Please, explain to me the correct opinion. May Allaah reward you.

All perfect praise be to Allaah, The Lord of the Worlds. I testify that there is none worthy of worship except Allaah, and that Muhammad, sallallaahu ‘alayhi wa sallam, is His Slave and Messenger.

Hadeeths of the Prophet, sallallaahu ‘alayhi wa sallam, are of different grades, including: Saheeh (Authentic), Hasan (Sound), Dha‘eef (weak) and Mawdhoo' (fabricated). The scholars of Hadeeth have studied and defined these different grades very well.

Muslims accept all that was narrated in Saheeh Al-Bukhari and Saheeh Muslim and scholars consider that the Hadeeths narrated by both Al-Bukhari and Muslim are the most authentic Hadeeths, then the Hadeeths narrated by Al-Bukhari alone, then the Hadeeths narrated by Muslim alone.

The authenticity of the Hadeeths narrated in Saheeh Al-Bukhari are unarguable, to the extent that Al-Haafith Abu Nasr As-Sijizi said that Islamic jurists and other scholars agreed that, if a man made an oath in the name of Allaah that all Hadeeths mentioned in Saheeh Al-Bukhari were unarguably said by the Messenger of Allaah, sallallaahu ‘alayhi wa sallam, then his oath is valid and does an not need expiation.

As for the allegation concerning Jihaad, it does not even deserve consideration. The five pillars of Islam are the most important acts of worship in Islam, as stated in a Hadeeth narrated by Al-Bukhari and Muslim. However, this does not mean that duties and obligations are confined to these five pillars, but Jihaad, encouraging good and forbidding evil, and dutifulness to parents are all established Islamic obligations. Jihaad is the highest peak of Islam, as described in the Hadeeth narrated by At-Tirmithi and Ibn Maajah .

As for the claim that the majority of Hadeeths are fabricated, it is a groundless allegation since the vast majority of Hadeeths that are narrated in the well-known books of Hadeeth are authentic.  These well-known books of Hadeeth include:

1-        Saheeh Al-Bukhari

2-        Saheeh Muslim

3-        Sunan At-Tirmithi

4-        Sunan An-Nasaa'i

5-        Sunan Abu-Daawood

6-        Sunan Ibn Maajah

7-        Musnad  of Imaam Ahmad

8-        Muwatta’ of Imaam Maalik 

9-        Saheeh Ibn Khuzaymah

10 - Saheeh Ibn Hibbaan

Moreover, the existence of deviated groups does not prove that the Hadeeths are distorted. On the contrary, attacking the Sunnah, rejecting and casting doubts upon it, and interpreting it in a way that contradicts its obvious meaning are the causes behind such a deviation.

Depending only on the Quran and rejecting most of the Sunnah is one of the opinions that formed the foundation of some deviated groups, such as the Jahmiyyah, the Mu‘tazilah, the Qur’aaniyyoon and others.

We advise you to know that the science of Hadeeth has rules and basics and no one has the right to judge a Hadeeth as Saheeh or Dha‘eef depending on mere imagination or doubts in the mind. Rather, the chain of narrators and the text of the Hadeeth or the tradition should be considered carefully in light of the rules and regulations set by the Islamic scholars throughout the centuries.

We also advise this person to be careful not to become an opponent of the Prophet, sallallaahu ‘alayhi wa sallam, by rejecting his Sunnah. He should know that Allaah The Exalted has undertaken the responsibility of preserving His religion and His book (the Quran) and this would be impossible if not accompanied by the preservation of the Sunnah of His Messenger, sallallaahu ‘alayhi wa sallam, which is a revelation like the Quran. Allaah The Almighty Says (what means):

• {Nor does he speak from [his own] inclination. It is not but a revelation revealed.} [Quran 53:3,4]

• {And We revealed to you the message that you may make clear to the people what was sent down to them.} [Quran 16:44]

Allaah Knows best.