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.
Reported by Abu Yaala (1084), and Ibn Hibban graded it sahih (823), both from the hadith of Uthman bin Abu Shayba, from Jareer, from Amash, from Abu Salih, from Abu Saeed, who said, then he mentioned it. Its chain of transmission is sahih.