What did Umar (RA) say was the reason why he allowed those with few camels and sheep to graze their livestock in the Hima, as mentioned in the hadith of the Prophet Muhammad (peace be upon him)?
 Narrated Aslam:                     `Umar bin Al-Khattab appointed a freed slave of his, called Hunai, manager of the Hima (i.e. a pasture devoted for grazing the animals of the Zakat or other specified animals). He said to him, "O Hunai! Don't oppress the Muslims and ward off their curse (invocations against you) for the invocation of the oppressed is responded to (by Allah); and allow the shepherd having a few camels and those having a few sheep (to graze their animals), and take care not to allow the livestock of `Abdur-Rahman bin `Auf and the livestock of (`Uthman) bin `Affan, for if their livestock should perish, then they have their farms and gardens, while those who own a few camels and those who own a few sheep, if their livestock should perish, would bring their dependents to me and appeal for help saying, 'O chief of the believers! O chief of the believers!' Would I then neglect them? (No, of course). So, I find it easier to let them have water and grass rather than to give them gold and silver (from the Muslims' treasury). By Allah, these people think that I have been unjust to them. This is their land, and during the prelslamic period, they fought for it and they embraced Islam (willingly) while it was in their possession. By Him in Whose Hand my life is! Were it not for the animals (in my custody) which I give to be ridden for striving in Allah's Cause, I would not have turned even a span of their land into a Hima."