The Messenger of Allah ﷺ said, "How can I find comfort when the bearer of the Trumpet has already placed it to his lips and bowed his forehead, waiting for the command to blow?"We said, "Messenger of Allah, what should we say on that day?"He replied, "Say, 'Allah is sufficient for us, and the best Disposer of affairs. Upon Allah we rely.'"
قال رسول الله ﷺ: كيف أنعم وصاحب الصور قد التقم، وحنا جبهته ينتظر متى يؤمر أن ينفخ. قيل: قلنا: يا رسول الله، ما نقول يومئذ؟ قال: قولوا: حسبنا الله ونعم الوكيل، على الله توكلنا.
Abu Yaala reported it (1084), and Ibn Hibban graded it sahih (823), both from the hadith of Uthman bin Abu Shayba, who said, we were told by Jareer, from Amash, from Abu Salih, from Abu Saeed, who then narrated the hadith. Its isnad is sahih. The discussion of it is set out in detail in the Book of Iman.