Taken from Non-Ahmadi website:
The Hadith about 73 sects [Archive] - sunniforum.com
The Messenger (SalAllahu ‘alaihi wasallam) said;
إفترقت اليهود على احدى وسبعين فرقة،
وافترقت النصارة على إثنتين وسبعين فرقة،
وتفترق أمتي على ثلاث وسبعين فرقة
“The Jews were divided among themselves into seventy one or seventy two sects, and the Christians were divided among themselves into seventy one or seventy two sects. And My Ummah will be divided among itself into seventy three sects.” Abu Dawood, at-Tirmidhi, al-Hakim and Ahmad among several others, reported this Hadith. At-Tirmidhi said; “Hadeethun Hassanun Sahih”.
In another variation, Imam Ahmad recorded that Abu Amir Abdullah bin Luhay said; "We performed Hajj with Mu`awiyah bin Abi Sufyan. When we arrived at Makkah, he stood up after praying Dhuhr and said; ‘The Messenger of Allah (SalAllahu alaihi wasallam) said;
إِنَّ أَهْلَ الْكِتَابَيْنِ افْتَرَقُوا فِي دِينِهِمْ عَلى ثِنْتَيْنِ وَسَبْعِينَ مِلَّةً، وَإِنَّ هذِهِ الْأُمَّةَ سَتَفْتَرِقُ عَلى ثَلَاثٍ وَسَبْعِينَ مِلَّةً يَعْنِي الْأَهْوَاءَ كُلُّهَا فِي النَّارِ إِلَّا وَاحِدَةً وَهِيَ الْجَمَاعَةُ وَإِنَّهُ سَيَخْرُجُ فِي أُمَّتِي أَقْوَامٌ تَجَارَى بِهِمْ تِلْكَ الْأَهْوَاءُ كَمَا يَتَجَارَى الْكَلَبُ بِصَاحِبِه، لَا يَبْقَى مِنْهُ عِرْقٌ وَلَا مَفْصِلٌ إِلَّا دَخَلَه
‘The People of the Two Scriptures divided into seventy-two sects. This Ummah will divide into seventy-three sects, all in the Fire except one, that is, the Jama’ah. Some of my Ummah will be guided by desire, like one who is infected by rabies; no vein or joint will be saved from these desires.’’”
This hadith was also narrated by Abu Dawood (2/503), Ahmad (4/102) and al-Haakim (1/128) among others, with similar wording but with the following addition;
ثنتان وسبعون في النار. قيل: يا رسول الله
من هم؟ قال: الجماعة
“Seventy two in hell fire and one in the Jannah: that is the ‘Jama’ah.’”