An elaborate system was developed by scientists of hadith to determine the authenticity of traditions based on “two premises”:

  1. that the authenticity of a hadith report is “best measured by the reliability of the transmitters” (rāwī pl. ruwāt) of the report;
  2. and that this reliability is best measured by “carefully scrutinizing” the “individual transmitters” of the hadith and “the continuity of their chains of transmission”.[16]

A basic element of hadith studies consist of a careful examination of the chain of transmission (sanad سند, also isnād اسناد, or silsila سِلْسِلَة), relaying each hadith from the Prophet to the person who compiles the hadith. The isnād and the commentary are distinct from the matn (متن), which is the main body, or text, of the hadith,[17][18] These two terms are the primary components of every hadith.

Source: Hadith studies – Wikipedia