سنن أبي داود

Narrated A man from the Companions of the Prophet:

Ubaydullah ibn Salman reported on the authority of a man from the Companions of the Prophet (ﷺ): When we conquered Khaybar, they (the people) took out their spoils which contained equipment and captives. The people began to buy and sell their spoils. When the Messenger of Allah (ﷺ) prayed, a man came to him and said: Messenger of Allah, I have gained today so much so that no one gained from this valley. He asked: Woe unto you, how much did you gain? He replied: I kept on selling and buying until I gained three hundred uqiyahs. The Messenger of Allah (ﷺ) said: I tell you a man who gained better than you. He asked: What is that, Messenger of Allah? He replied! Two rak'ahs (of supererogatory prayer) after the (obligatory) prayer.