حَدَّثَنَا مَحْمُودُ بْنُ غَيْلاَنَ، حَدَّثَنَا وَكِيعٌ، حَدَّثَنَا سُفْيَانُ، عَنْ أَبِي إِسْحَاقَ، عَنِ الْمُهَلَّبِ بْنِ أَبِي صُفْرَةَ، عَمَّنْ سَمِعَ النَّبِيَّ صلى الله عليه وسلم يَقُولُ ‏"‏ إِنْ بَيَّتَكُمُ الْعَدُوُّ فَقُولُوا‏:‏ حم لاَ يُنْصَرُونَ ‏"‏ ‏.‏ قَالَ أَبُو عِيسَى وَفِي الْبَابِ عَنْ سَلَمَةَ بْنِ الأَكْوَعِ ‏.‏ وَهَكَذَا رَوَى بَعْضُهُمْ عَنْ أَبِي إِسْحَاقَ مِثْلَ رِوَايَةِ الثَّوْرِيِّ وَرُوِيَ عَنْهُ عَنِ الْمُهَلَّبِ بْنِ أَبِي صُفْرَةَ عَنِ النَّبِيِّ صلى الله عليه وسلم مُرْسَلاً ‏.‏

Narrated Al-Muhallab bin Abi Sufrah: From one who heard the Prophet (PBUH) saying: "If you suffer a surprise attack from the enemy then say: 'Ha Min, they will not be victorious.'" [Abu 'Eisa said:] There is something on this topic from Salamah bin Al-Akwa'. This is how some of them reported it from Abu Ishaq, the same as the narration of Ath-Thawri. And it has been reported from him, from Al-Muhallab bin Abi Sufrah from the Prophet (PBUH) in Mursal form. Translation Not Available

Book Ref: Jamiya Tirmidhi Book 23 Hadith 1682
Web Ref:  Jamiya Tirmidhi Vol 3 Book 21 Hadith 1682