Hadith 31-302

وَبِإِسْنادِهِ عَنْ عَلِيِ‏ عَلَيْهِ السَّلامُ قالَ: قالَ النَّبِيُ‏ صَلَّى اللهُ عَلَيْهِ وَآلِهِ: عَمّارٌ عَلَى الحَقِّ حِينَ يُقْتَلُ بَيْنِ الفِئَتَيْنِ، إِحدَى الفِئَتَيْنِ عَلَى سَبِيلِي وَسُنَّتي؛ وَالاُخْرى‏ مارِقَةٌ مِنَ الدِّينِ، خارِجَةٌ عَنْهُ.

According to the same documentation, on the authority of Ali (a.s.) the Prophet (S) said, “Once Ammar is killed, when he is caught between the two factions - one who abides by my way and traditions, while the other faction has departed from my religion - he is adhering to the right religion.”