Numbers 33:13

And they departed from Dophkah, and encamped in Alush. The strong fort, as the Targum of Jonathan calls it; this was twelve miles from Dophkah: according to the Jewish chronology d, this Alush is the wilderness of Sin, where the Israelites came on the fifteenth day of the seventh month from their going out of Egypt; and they say, that in Alush the sabbath was given them, and that there they kept the first sabbath, as it is said,

and the people rested on the seventh day, Exodus 16:30.

d Seder Olam Rabba, c. 5. p. 17.