Mishkat al-Masabih
Mishkat al-Masabih 1325
Optional Prayer - Section 2
Arabic hadith text
وَعَنْ حُذَيْفَةَ قَالَ: كَانَ النَّبِيُّ صَلَّى اللَّهُ عَلَيْهِ وَسَلَّمَ إِذَا حَزَبَهُ أَمْرٌ صَلَّى. رَوَاهُ أَبُو دَاوُد
Translation
Hudhaifa said that when anything distressed the Prophet he prayed. Abu Dawud transmitted it.