What is the validity of what my Shia friend mentioned concerning Umar ibn al-Khattab's statement during the Prophet Muhammad's illness: "The Messenger is under the influence of fever, and perhaps he does not know what he is saying; we have the Qur'an, and it is the Book of Allah, sufficient for us," and about its presence in Sahih al-Bukhari, Part 4, Page 4? And did Umar ibn al-Khattab believe that he was not bound by the Sunnah of the Messenger, and that he could declare lawful what Allah has forbidden and declare forbidden what Allah has made lawful?

It is not as the impudent Shiite understood. The saying of the one who said, "Is he delirious?" was a refutation of whoever hesitated in obeying the command of the Prophet, peace and blessings be upon him, not an accusation of delirium against him, for he is infallible in all his states. As for 'Umar's statement, "The Book of Allah is sufficient for us," it stemmed from his profound understanding and keen foresight, fearing that they might be burdened with what they could not bear. The Prophet's, peace and blessings be upon him, leaving off any denouncement of him indicates approval of his opinion. As for the claim that 'Umar opposed the Sunnah (definition), it is false, for 'Umar was an imitator and follower of the Sunnah. He was an inspired man whose opinion concurred with revelation. He attained such knowledge and virtue as no one else had, except for the truthful one (Abu Bakr).