ما كنا نعرف المنافقين على عهد رسول الله صلى الله عليه وسلم إلا ببغض علي.
We did not recognise the Munafiqin in the time of the Messenger of Allah salla Llahu ‘alayhi wa sallam except by means of their hatred for ‘Ali.
This hadith has been transmitted from Abu Sa’id al Khudri, Abu Dharr, and Jabir ibn ‘Abdullah radiya Llahu ‘anhum. I will restrict myself to the version of Abu Sa’id al Khudri radiya Llahu ‘anhu because it is (the only) authentic version.
Al Himyari narrates — Harun ibn Ishaq narrated to us — Sufyan ibn ‘Uyaynah reported to us — from al Zuhri — from Yazid ibn Khusayfah — from Busr ibn Sa’id — from Abu Sa’id al Khudri radiya Llahu ‘anhu.
This chain of transmission is Hassan (fair). All of the narrators of this hadith appear in Imam al Bukhari’s collection as well as Imam Muslim’s collection, except for Harun ibn Ishaq al Kufi; he appears in the collections of al Tirmidhi, al Nasaʾi, and Ibn Majah. Abu Hatim said (about him), “He is saduq (sincere).” Al Nasaʾi says (about him), “He is a thiqah (reliable).”
Abu Bakr al Suli and Abu Nuaim narrate this hadith via a different chain of transmission from Abu Sa’id al Khudri.
All the other versions have been mentioned in the original work. Each of these versions contains flaws. Ibn Taymiyyah mistakenly ruled this hadith a fabrication. I have explained his mistake in the original work.
 Abu Bakr al Suli: Juz Min Ahadith Abi Bakr al Suli, hadith no. 1174; Abu Nuaim: Sifat al Nifaq wa Na’t al Munafiqin, 80.
 Ibn Taymiyyah: Minhaj al Sunnah al Nabawiyyah, 4/286.