The Companions learned the Qur'an from the Prophet, witnessed its historical setting and knew the Arabic usage in which the first revelation came. Their understanding is consequently an important foundation of tafsir.
Prophetic supplications reported for Ibn ʿAbbās include Allāhumma ʿallimhu al-kitāb and Allāhumma ʿallimhu al-taʾwīl—prayers for his understanding of the Book and its interpretation. They demonstrate the great value of this knowledge.
Care is still needed to distinguish a report traced to the Prophet, an interpretation from a Companion, and cases where multiple transmitted explanations exist. Scholarly evaluation of reports remains necessary.