Ibrâhîm b. ‘Abd Al-Rahmân b. ‘Auf reports:
‘Umar b. Al-Khattâb – Allah be pleased with him – was given the treasures of the Persian Emperor (after his conquest), ‘Abdullah b. Arqam asked, “Are you going to put this into the public treasury (bayt al-mâl) until you can distribute it?” ‘Umar replied, “No by Allah, I will not take this under a roof before I have passed it on.” So they put it in the middle of the mosque and spent the night guarding it. In the morning, ‘Umar uncovered the treasure and saw such an amount of gold and silver that it almost shone; so he began to cry. ‘Abd Al-Rahmân b. ‘Auf – Allah be pleased with him – said, “Why do you cry o Amîr of the Believers? This is a day of thanks and a day of happiness for sure.” ‘Umar replied, “Woe to you, this has never been given to a people except that it has cast enmity and hatred amongst them.”
Ibn Al-Mubârak in Al-Zuhd wa Al-Raqâ`iq Vol. 2 p595, 596.