How can we tell the saheeh ahaadeeth from the fabricated ones?

I have a question regarding hadith. I know we should follow Muhammad's( ) example but how sure are we that some of the hadith we have today are not corrupt and changed. I am by no means judging the hadith and saying they are wrong. please understand that. it's just that some muslims have told me alot of hadith is changed and bogus. I follow the hadith to the best of my ability. Please help me with any knowledge. thank you.

Praise be to Allaah.

Allaah has guaranteed to protect His religion, which includes preserving His miraculous Book, and preserving the Sunnah of His Prophet which helps us to understand the Qur’aan. Allaah says (interpretation of the meaning):

“Verily, We, it is We Who have sent down the Dhikr (i.e. the Qur’ân) and surely, We will guard it (from corruption).” [al-Hijr 15:9]

The word Dhikr here includes both the Qur’aan and the Sunnah.

Many people – in the past and at present – have tried to insert weak and fabricated ahaadeeth into the pure sharee’ah and the Prophetic Sunnah. But Allaah has thrown their plots back in their faces and has provided means of protecting His religion. Among these means are the trustworthy and reliable scholars who sifted through the reports and checked their sources, examining the biographies of the narrators and even describing the point at which a narrator began to be confused in his narration, and stating who narrated from him before he became confused and who narrated from him afterwards. They described the journeys of the narrator, which cities he visited and from whom in each city he took reports. They checked many details about each narrator, more than can be listed here. All of this indicates that the religion of this Ummah is protected, no matter how hard our enemies try to plot and play about with the religion and distort it.

Sufyaan al-Thawri said: the angels are the guardians of the heavens and the scholars of hadeeth are the guardians of this world.

Al-Haafiz al-Dhahabi mentioned that Haaroon al-Rasheed was about to execute a zindeeq (heretic), and the zindeeq said: “What are you going to do about the one thousand ahaadeeth I have fabricated?” Al-Rasheed said: “What are you going to do, O enemy of Allaah, about Abu Ishaaq al-Fazaari and ‘Abd-Allaah ibn al-Mubaarak, who will sift through those ahaadeeth and examine them letter by letter?”

The seeker of knowledge can find out about the fabricated (mawdoo’) and weak (da’eef) ahaadeeth very easily, by looking at the isnaads or chains of narrators, and finding out about the people mentioned there in the “books of men” i.e., narrators (kutub al-rijaal) and the books which state which narrators are sound or otherwise (kutab al-jarh wa’l-ta’deel).

Many scholars have compiled these fabricated and weak ahaadeeth in books devoted solely to these type of reports, so that it is easy to find out about them – then one can beware of them and warn others about them. These books include al-‘Ilal al-Mutanaahiyah by Ibn al-Jawzi, al-Manaar al-Muneef by Ibn al-Qayyim, al-La’aali’ al-Masnoo’ah fi’l-Ahaadeeth al-Mawdoo’ah by al-Suyooti, al-Fawaa’id al-Majmoo’ah by al-Shawkaani, al-Asraar al-Marfoo’ah fi’l-Ahaadeeth al-Mawdoo’ah by Ibn ‘Arraaq, and Da’eef al-Jaami’ al-Sagheer and Silsilat al-Ahaadeeth al-Da’eefah wa’l-Mawdoo’ah, both by Shaykh al-Albaani, may Allaah have mercy on him.

The fact that the brother has heard about weak and fabricated ahaadeeth indicates that he is making the distinction – praise be to Allaah – between what is saheeh and what is not. This is by the grace of Allaah, and is a sign that Allaah is protecting this sharee’ah, as we mentioned above.

We advise our brother to read the “books of men” i.e., narrators (kutub al-rijaal), the books which state which narrators are sound or otherwise (kutab al-jarh wa’l-ta’deel) and the books of the science of hadeeth (kutub mustalah al-hadeeth), so that he can learn the extent of the efforts made by the scholars in the service of the Sunnah.

And Allaah is the source of strength.