Musar su Genesi 20:16

How did G–d prove that point? Whereas in the days of Anah a mule had to be the product of crossbreeding, Isaac became the owner of mules which were not the result of crossbreeding but a heavenly gift. Even the scoffers who lived around him became aware of this. This is why Isaac became "great" in their eyes. They realised that if G–d performs such miracles with the livestock of a צדיק, how much greater would be the miracles He would perform with the צדיק himself! When the people said that the dung of Isaac's mules was worth more than the silver and gold of Avimelech, they meant that the fact that Isaac possessed mules which were not the result of crossbreeding proved more about his status as a holy man than the thousand silver pieces Avimelech had given to Sarah to demonstrate that her virtue had not been compromised while she was in Avimelech's palace (Genesis 20,16). Why does the Midrash quote the Philistines as also referring to Avimelech's gold? The Torah does not report Avimelech giving gold to either Sarah or Abraham! We need not understand the word כסף, silver, in the Torah as silver literally, but as an expression of the value of the gift in terms of silver coins. We now have demonstrated how the gift of the land of Israel is specifically connected with Isaac.