Yazid bin Abi Habib (may Allah have mercy on him) said that Sayyiduna Umar (may Allah be pleased with him) wrote to Sa'd (may Allah be pleased with him) at the time of the conquest of Iraq: After praise and glorification: Your letter has reached me, in which you mention that the people ask you to divide the spoils of war among them, and what Allah has granted you as fay'. When my letter reaches you, look at whatever horses or wealth the people have brought to you in the camp, and divide it among the Muslims who are present. Leave the lands and the rivers to those who work them, so that (their revenue) goes into the stipends of the Muslims. If you divide them among those present, nothing will remain for those who come after them.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب السير / 18369