[Pooya/Ali Commentary 3:138] Those who are aware of the boundaries laid down by Allah, guard themselves against evil and take refuge with Allah, alone can understand and teach the Quran. See commentary of muttaqin in verses 2 and 177 of al Baqarah. Shirk (polytheism) is the greatest evil. The Holy Prophet and his Ahl ul Bayt, historically, were the only persons who never worshipped any one other than Allah, therefore, it is the will of Allah that mankind should learn the meaning and purport of the Quran from the Ahl ul Bayt, confirmed by the Holy Prophet in his farewell address to the nation (hadith al thaqalayn).