Anyway...
Anyway, this verse needs further discussion, which we are going to undertake later. There are other verses which concern the event of Ghadir. This event itself is a part of the Islamic traditions, but we are going to discuss it later. One of the verses revealed in connection with the event of Ghadir says: "0 Messenger!
Make known that which has been revealed to you from your Lord, for if you do it not, you will not have conveyed His message."(Surah al-Mai'dah, 5:67) The tone of this verse is as serious as that of the tradition: "He who died and did not recognize the Imam of his time, died a pre-Islamic death." Briefly it may be said that the verse itself shows that its subject is so important that if the Prophet does not make it known, that would mean that he has not conveyed the message of Allah at all.
The Shi'ah and the Sunnis agree that Surah al-Mai'dah is the last surah (chapter) revealed to the Holy Prophet, and this verse is one of the last verses of this surah. In other words it was revealed when the Holy Prophet had already conveyed all other injunctions and teachings of Islam during his 13 years' stay in Makkah and 10 years' stay in Medina as the Prophet. This verse was among the last instructions of Islam.
Now the Shi'ah ask what that instruction could be which was so important that if it was not conveyed all that the Holy Prophet did in the past would become void. You cannot indicate any subject connected with the last years of the Holy Prophet's life which may be so important. But we say that it is the question of Imamat, which is so important that if Imamat is lost, nothing remains. Without Imamat the whole structure of Islam would crumble down.
Moreover, the Shi'ah cites the reports and the traditions of the Sunnis themselves in support of their claim that this verse was revealed in connection with the Ghadir Khum event.
In Surah al-Ma'idah itself there is another verse which runs as follows: "This day have I perfected your religion for you, completed My favour to you and have chosen Islam for you as religion." (Surah al-Ma'idah, 5:3) This verse shows that on that day something happened, which was so important that it perfected religion, completed Allah's Favour to mankind and without which Islam could not be as Allah wanted it to be.
The Shi'ah argue that the stringent tone of the verse shows that the thing to which it refers is so important that the very existence of Islam as a true religion depends on it.