The most important event of 10th Hijri was Hujjatul Wada’a.
There are different names of Hujjatul Wada'a, Hujjatul Wada'a, Hujjatul Atmaam, Hujjatul Balagh, Hujjatul Islam, etc. It is commonly known as Hujjatul Wada’a (the Farewell Hajj) because the Holy Prophet (Sallallahu alaihi wa sallam) took farewell from the Ummah on this occasion.
Although, there were not many facilities and comforts in travel, Companions from all over the world came to undertake the Hajj. As per one narration, 124,000 and as per another 114,000 Companions were present on this occasion. Such a huge congregation did not gather before the Holy Prophet (Sallallahu alaihi wa sallam) after this. For many of those who came, from the earthly point of view, it was the farewell visit. That is why, it is called Hujjatul Wada’a.
On the 9th of Dhul Hijjah, the following verse of the Holy Quran was revealed about the completion and perfection of Islam:
Today I have perfected your Din (Religion) for you, and have completed My Blessing upon you, and have chosen for you Islam (as) Din (a complete code of life). Surah Maida (5:3)
This is called as Hujjatul Balagh because in the sermon of this Hajj, the Holy Prophet (Sallallahu alaihi wa sallam) demanded those who were present to testify that He had completed the propagation (Tableegh) of Prophethood. He (Sallallahu alaihi wa sallam) made them witness and said: The one who is present should convey to the one who is absent. (Seerat Halbiya, Vol. 3, Pg. No. 282/283)
It is called as Hujjatul Islam because the Holy Prophet (Sallallahu alaihi wa sallam) described the essence of the Islamic teachings on this occasion.