One of the verses related to appointment of Imam Ali to imamate in the day of Ghadir is verse 3 of Al-Maidah. There are controversies among the Fariqain’s commentators about revelation and determining occurrence of this verse. Citing verses and hadiths, the Shiite commentators explicitly believe that this verse is about announcing Imam Ali’s Vilayat and succession on the day of Ghadir, but some of the Sunnis’ commentators assert that the day of Arafah is the time of revelation of this verse and they believe that it is the day of completion of God’s ordinances, statutes and traditions so that no other ordinances from god’s statutes have been revealed to the Holy Prophet and religion has been completed. Some other Sunnis’ scholars believe that the verse is revealed in the day of Ghadir and it is related to Imam Ali’s succession. Analyzing the commentary viewpoints and opinions of some commentators such as S’alabi, Razi, Siyuti, Alousi, and Zahili, the paper addresses the verse of “Ikmal” by criticism and makes it easy to prove the Shiite commentary thought which is the same as confirming Imam Ali’s Imamate and Vilayat.