أَخْبَرَنَا عَمْرُو بْنُ عَلِيٍّ، قَالَ حَدَّثَنَا يَحْيَى، قَالَ حَدَّثَنَا شُعْبَةُ، قَالَ حَدَّثَنَا زِيَادُ بْنُ عِلاَقَةَ، عَنْ عَرْفَجَةَ، قَالَ سَمِعْتُ رَسُولَ اللَّهِ صلى الله عليه وسلم يَقُولُ ‏"‏ سَتَكُونُ بَعْدِي هَنَاتٌ وَهَنَاتٌ فَمَنْ أَرَادَ أَنْ يُفَرِّقَ أَمْرَ أُمَّةِ مُحَمَّدٍ صلى الله عليه وسلم وَهُمْ جَمْعٌ فَاضْرِبُوهُ بِالسَّيْفِ ‏"‏ ‏.‏

It was narrated that 'Arfajah said: "I heard the Messenger of Allah [SAW] say: 'After me there will be many calamities and much evil behavior. Whoever wants to create division among the Ummah (of Muhammad [SAW]) when they are all united, strike him with the sword.'" Translation Not Available

Book Ref: Sunan An Nisai Book 37 Hadith 4022
Web Ref:  Sunan An Nisai Vol 5 Book 37 Hadith 4027