Difference on reference of the pronoun in ansahu, forgot him in the verse 42 of R`ad has turned it to one challengeable verse in the field of commentary and theology. In traditional commentary relying on a great number of traditions, Yusuf a. has been taken as the reference of the mentioned phrase and his demand has been introduced to be a wrong action being a cause for his forgetting God`s remembrance. Some of commentators have known the reference the man in prison with Yusuf who affected by Satan forgot Yusuf remembrance before the king. The paper, weakening the validity of traditions in the field in both sides of matter and line of transition, reviewing different views, and relying on the context of verses and the Quranic manner of mentioning messengers` cases of errors being followed by their penitence, has viewed the reference to be the man in prison with Yusuf and, therefore, the prophet has known pure of forgetting.