Only one Firqah will go to Jannah and the others 72 will go to hell

Therefore, the holy Prophet (Sallal Laahu ‘Alaiehi Wa Sallam) said, “My Um-mat will be divided into 73 factions, one of this will go to Heaven and 72 will go to Hell.” The Companions of the Prophet (Ridwaanul Laahi Ta’aalaa ‘Alaiehim Ajma’een) said, O Prophet of Allaah! (Sallal Laahu ‘Alaiehi Wa Sallam) which one will be that salvated group? The holy Prophet (Sallal Laahu ‘Alaiehi Wa Sallam) said, “It would be the Naajiyah group, which would follow my way and the way of my companions.” (Tirmizee, Abu Daawood, Ibne Maajah).
It is also mentioned in Ibne Maajah, one of the six famous authentic books of Ahaadees that Hazrat Anas bin Maalik (Radiyal Laahu ‘Anhu) related that he heard the holy Prophet (Sallal Laahu ‘Alaiehi Wa Sallam) say, “My Um-mat would never unite on a deviation, when you see differences (in the Um-mat), you obligatory hold fast to the largest group.”(The group of magnificence)

These Ahaadees makes it clear to us that one of the groups into which Um-mat-e-Muhammadi (‘Alaa Saahibhas-Salaatu Was-Salaam) would be divided it would be the largest group and we have been ordered to totally hold fast to this group, only that is the group which will be going to Heaven and beside this all the rest will be worthy of going to Hell. The holy Prophet (Sallal Laahu ‘Alaiehi Wa Sallam) has done us a great favors, by informing us also about the signs of this salvated group (Naajiyah). Otherwise every group would be claiming itself to be the Naajiyah group. It is clear that Naajiyah group is not a separate sect and in no way holding on to their beliefs, actions and preaching or promoting them can be considered as indulging in factionalism.
Readers may, perhaps, say that despite this clear saying of the holy Prophet (Sallal Laahu ‘Alaiehi Wa Sallam) every group calls itself Naajiyah. In reply, let me say that no claimant can be truthful about his claim unless he produces valid arguments in support to his claim and unless he proves the truth of his claim through the Qur’aan and the Sunnat. The holy Prophet (Sallal Laahu ‘Alaiehi Wa Sallam) has clarified that the Naajiyah group would be the largest and (the noblest group) and has urged us to associate with it and has also told us about its signs, it would be following his way and the way of his companions (Radiyal Laahu Ta’aalaa ‘Anhum).
On the basis of these sayings of the Holy Prophet [Peace be upon Him] the Naajiyah group is titled as ‘Ahle Sunnat Wa Jamaa’at’, or in one word, “Sun-nee” (meaning this is the group whose beliefs and acts are according to the ways of the holy Prophet (Sallal Laahu ‘Alaiehi Wa Sallam) and of his companions (Radiyal Laahu ‘Anhum).
Notes…
Naajiyah is derived from the word Nijaat..[Salvation]
“My Ummah will divide into seventy-three different sects, only one sect will be  ahl an–najaat (people of salvation)”….called Naajiyah group.