The rate of jizya that were fixed and implemented by the second caliph of the Rashidun Caliphate, namely 'Umar bin al-Khattab, during the period of his Khilafah, were small amounts: four dirhams from the rich, two dirhams from the middle class and only one dirham from the active poor who earned by working on wages, or by making or vending things. The 13th-century scholar Al-Nawawī writes, "The minimum amount of the jizya is one dinar per person per annum; but it is commendable to raise the amount, if it be possible to two dinars, for those possessed of moderate means, and to four for rich persons." Abu 'Ubayd insists that the "dhimmis" must not be burdened beyond their capacity, nor must they be caused to suffer.