yuksel also argues, “if the signature of narrators (sanad) cannot provide authenticity about the source of hadith, then, our only guide to decide on the content of hadiths (matn) will be our personal wish or our current inclinations. how can we decide which hadith has a merit? how can we decide which hadiths is accurate? we may say ‘by comparing them with the Quran!’” he again betrays his ignorance with regards to this islamic branch of knowledge concerning hadeeths. there are two main considerations when judging the authenticity or weakness of a hadeeth. the first is its sanad; its chain of transmission from the one who originally uttered the report to the one who finally recorded it in his book. this consideration determines the validity of the source. the second consideration is the matn (text); its main body and the content of the report. this consideration doesn’t determine the validity of its source, but rather the validity of what’s being reported. there are many narrations that have weak chains of narration, but contain correct information. such narrations can be strengthened by bringing other narrations similar to it conveying the same information as support.
as for how we determine which hadeeths have merit and which don’t, then that is where the islamic “sciences of hadeeth and their narrators” come in. for one to determine for himself which hadeeths are authentic and which ones are weak, he must first study the sciences related to hadeeth and its narrators, starting with the books of mustalah (terminologies) which contain the definitions used by the scholars of this field. there are also the many books of biographies that one must refer to to become acquainted with the various narrators of hadeeth; where and when they were born, who their teachers were (i.e., who they narrated from), who their students were (i.e., who narrated from them), whether they wrote their narrations down or memorised them, whether they made mistakes or used to forget certain details in the hadeeths they would narrate, whether they had any heretic beliefs or were known to lie or were accused of lying. then of course, there are the many, many compilations and collections of hadeeths that one needs to be familiar with to compare various narrations from certain narrators in order to study their tendancies and habits in narrating (i.e., did they narrate from meaning or word for word), did they narrate bits and parts of certain hadeeths to some and the complete versions to others and other such things. if one is not able to study these sciences extensively to get familiar with narrations and those who narrated them, then one must rely upon the judgements of qualified scholars who have done this, just as Allah has commanded the muslims in the Quran, “then ask the people of the remembrance if you do not know,” meaning, ask the people of knowledge, the scholars if you don’t know.
as for the assertion that the Quran is all we need, then this is refuted by the Quran itself, which also directs us to the sunnah (the way and teachings) of prophet muhammad, which is derived from the collective body that what is known as hadeeth. Allah says, “and whatever the messenger gave you then take it, and whatever he prohibited you from then obstain.” He also says, “your companion (i.e., muhammad) has not strayed, nor erred and he does not speak from desire. surely, it is but revelation revealed.” He also says, “and certainly there has been a good example for you in Allah’s messenger for whoever hopes for Allah and the Last Day and remembered Allah much.” as well as, “We sent to you a messenger amongst you reciting to you Our verses, purifying you and teaching you the Book (i.e., the Quran) and the wisdom (i.e., the sunnah) and teaching you what you did not know.”
there are many other verses that are evidence for the obligation of following the sunnah of prophet muhammad but this should suffice.