Exodus 15:22

The wilderness of Shur. This is the desert region reaching from the eastern border of Egypt to the southern border of Palestine, and touching in the south the mountains of the Sinai Peninsula. It is mentioned several times in the patriarchal narratives (Gen. 16:7; 20:1; 25:18), and in the records of Saul’s and David’s victories over the Amalekites (1 Sam. 15:7; 27:8). It was through the southern part of this desert that Israel marched, in a southeasterly direction along the shores of the Red Sea. In Num. 33:8 this region is called the “wilderness of Etham.” If the interpretation given in the comment on Ex. 13:20 is correct, that Etham is an Egyptian word for a border fortress, it is easy to understand why the desert of Shur should also be called the desert of Etham.

Found no water. The Israelites, no doubt, carried a supply of drinking water in leather pouches, as Oriental peoples from ancient times have done. Knowing they were to enter the desert, the Israelites would not fail to take water with them, but a march of three days without finding more to replenish their exhausted supply would bring suffering to both man and beast. It was therefore imperative that they find wells or springs at certain intervals. Of all domestic animals used in the Near East the donkey was the most widely employed beast of burden for desert travel. The camel was found only occasionally prior to the 12th century B.C. Donkeys are able to travel for four days without water, but cattle, which the Israelites possessed in great numbers, could not possibly live without more frequent watering. For this reason a march of three days without finding water was about the limit the cattle could endure and not perish.