Why Only One Sect Out of 73 Will Enter Paradise
7-3-2019 | IslamWeb
Question:
Salam. Dear Scholars. I always wanted to know why only one sect will enter paradise? Why only one out of 73? Aren't the other sects following the Quran and the Sunna? All muslim sects claim they follow the Sunna and Quran, dont they? So why should only one enter paradise?
Answer:
All perfect praise be to Allah, The Lord of the Worlds. I testify that there is none worthy of worship except Allah, and that Muhammad 
is His slave and Messenger.
First of all, it should be mentioned that the Islamic sects who will enter Hellfire because of deviating from the guidance of the Prophet will ultimately enter Paradise even if they have entered Hellfire beforehand. Their matter is like those who have the principle of faith and died upon Tawheed (belief in Allah and worshipping Him Alone without associating with Him any partners).
As for your question: Why is it that only one sect will enter Paradise? The answer to this question is deduced from the Hadeeth itself that states that the Muslim nation will split up into 73 sects.
The saved sect is the one that adheres to the Quran and the Sunnah, and which is upon the methodology of the majority of the (Muslim) nation and do not deviate from it until they meet Allah whilst upon this state.
Shaykh Ibn Taymiyyah 
said:
"This Hadeeth is authentic and is well-known in the books of Sunnah and in the Masaanid (plural of Musnad), such as the Sunnah of Abu Daawood, At-Tirmithi, An-Nasaa’i, and others. The wording of the Hadeeth is as follows:
'The Jews were split up into seventy-one sects, all of whom will be in Hellfire except one; the Christians were split up into seventy-two sects, all of whom will be in Hellfire except one; and my nation will split up into seventy-three sects, all of whom will be in Hellfire except one.'
Another narration reads: "They asked: 'O prophet of Allah, who will be the saved sect?' He replied: 'Those who will remain on the path which I and my companions are on today.'"
Yet, another narration reads: "They are the Jamaa’ah (the main body of Muslims); the Hand of Allah is with the Jamaa’ah."
It is for this reason that the Prophet, sallallaahu ‘alayhi wa sallam, described the saved sect as the Ahlus-Sunnah wal-Jamaa’ah, who are the overwhelming multitude and the great majority of the Muslims. The other sects are followers of aberrant views, schism, innovations and deviant desires. [….] The sign with which these sects are known is contradicting the Quran, the Sunnah, and the consensus of the scholars. Whoever acts according to the Book of Allah, the Sunnah, and the consensus (of the scholars), then he is from Ahlus-Sunnah wal-Jamaa’ah.'" [End of quote]
However, not everyone who claims to follow the Quran and the Sunnah is really following them in reality. Rather, some sects that are affiliated with Islam do not claim to follow the Sunnah at all. Some of them openly reject the Sunnah in its totality and in its details. Some of them accept its wording but reject its meaning and application, and yet some accept some of it and reject some of it. There are those who misinterpret it and explain it in a way that is contrary to its meaning and rulings. Of course, elaborating on this issue needs more details but this is not the place.
Since the above is known, then the most important reason for the emergence of sects and the emergence of misguiding innovations becomes known.
We hope that this answer is sufficient.
For more benefit, please refer to Fataawa 12682, 81638, 82163, 33503 and 322.
Allah knows best.