Then came Amalek,.... The Amalekites, who were not the posterity of Amalek, a son of Eliphaz, the son of Esau, by Timna the concubine of Eliphaz, Ge 36:12 who dwelt in the desert, to the south of Judea, beyond the city Petra, as you go to Aila, as Jerom says ; and so the Targum of Jonathan describes them as coming from the south; and Aben Ezra interprets them a nation that inhabited the southern country.
Josephus calls them the inhabitants of Gobolitis and Petra; but they were the descendants of Cush, and the same with those who were in Abraham's time long before Amalek, the descendant of Esau, was in being, Ge 14:7 and who bordered eastward on the wilderness of Shur:and fought with Israel in Rephidim; so that this was before they came from hence to Sinai, very probably as they were on the march thither, and before the rock was smitten, and they had been refreshed with water, and so while they were in distress for want of that, and therefore this must be a great trial and exercise to them.
What should move the Amalekites to come and fight with them, is not easy to say; it is by many thought to be the old grudge of the children of Esau against the children of Israel, because of the affair of the birthright and blessing which Jacob got from Esau, who were now on their march for the land of Canaan, which came to him thereby: but it is hardly probable that these people should know anything of those matters at this distance, and besides were not of the race of Esau; and if anything of this kind was in remembrance, and still subsisted, it is most likely that the Edomites would have been concerned to stop them, rather than these: it is more probable, that these had heard of their coming out, of Egypt with great riches, the spoils of the Egyptians; and being an unarmed, undisciplined people, though numerous, thought to have taken this advantage against them of their distress and contentious, and plundered them of their wealth; unless we can suppose them to be an ally of the Canaanites, and so bound by treaty to obstruct their passage to the land of Canaan: but be it as it may; they came out against them, and fought with them without any provocation, the Israelites not attempting to enter their country, but rather going from it; for these seem to follow them, to come upon the back of them, and fall upon their rear, as appears from De 25:17.
De locis Hebr. fol. 87. M. Antiqu. l. 3. c. 2. sect.