That outstanding event was the Messenger's Declaration at Ghadir Khum.

That outstanding event was the Messenger's Declaration at Ghadir Khum. While he was coming back from the valedictory pilgrimage to Medina he stopped at that place to tell the thousands of pilgrims who were accompanying him that ‘Ali Ibn Abu Talib is the "Mawla" (guardian) of every believer. Al-Hakim through his channel to Abu-Tufail reported that Zayd Ibn Arqam said: "When the Messenger of God was coming from the Valedictory pilgrimage he stopped at Ghadir Khum.

He ordered the pilgrims to sweep what was under the trees at that place. Then he said: 'I am about to be summoned by God and I shall respond. I am leaving among you the two valuables. One of the two is…