Ulum al Qur'an
Tafsir bi-l-riwaya
By this is meant all explanations of the Qur'an which can be traced back through a chain of transmission to a sound source, i.e.:
Naturally, the explanation of the Qur'an by the Qur'an and the explanation of the Qur'an by the Prophet are the two highest sources for tafsir, which cannot be matched nor superseded by any other source. Next to these rank the explanations by the sahaba, since the sahaba were witnesses to the revelations, were educated and trained by the Prophet himself and were closest to the period of the first Muslim umma. Of course all reports of explanations by the Prophet or by a sahabi must be sound according to the science of riwaya as in 'ulum al-hadith.