Al Adab al-Mufrad authentication by Shaikh Al Albani

The importance of this subject:
The knowledge of usūl al-hadīth is a science that serves the radiant Prophetic traditions; with it one can distinguish the Prophetic narrations in terms of authenticity and fabrication, soundness and weakness.
Al-Imām ‘Abdullāh ibn al-Mubārak said, “The quality of the hadīth is not in the conciseness of the isnād, rather its quality lies in the soundness of its narrators.”