Commentator`s interpretative methods is known as one origin for Shiite and Sunni difference in Quran commentaries. Commentators, when interpreting the verses 22-26 of chapter Suad, differ in conciliating prophet Dawood`s purity and wrong. Surveying Shiite and Sunni`s commentary methods comparatively, the paper has intended to study the origins of commentator`s differences. To do so, some Shiite and Sunni`s commentaries including Shiite commentaries   Al-Tebyan, Noor al-Thaqalayn and Al-Mizan  and Sunni`s Jami al-Bayan, Mafatih al-Ghaib, Ruh al-Ma'ani and      Al-Munir have been studied with regard to the subject. It has been proved that Al-Mizan, taking the method of Quran to Quran commentary and using reasonable and theological proofs and traditions as supporter, has presented the solution best.