From BiblePortal Wikipedia

Fausset's Bible Dictionary [1]

Zared or Zered (more accurately), Valley OF; or brook or watercourse of ( Numbers 21:12;  Deuteronomy 2:13-14). Running into the Dead Sea at the S.E. corner: the boundary between the districts of Jebal and Kerek: now Wady El Ahsy , between Moab and Edom (Robinson Bib. Res., 2:157), containing a hot spring called by the Arabs "the bath of Solomon." The limit of Israel's wandering; marking the time of the wilderness sojourn on one side as Kadesh did on the other.

The Speaker's Commentary identifies it with Wady Ain Franjy , the main upper branch of Wady Kerak ; the first western brook that crossed Israel's line of march. So the name marked an era in their progress; and the summons to cross it is noted in  Deuteronomy 2:13-14. Zered means "osier"; and Wady Safsaf , "Willows Brook", is given to the tributary joining Wady Ain Franjy below Kerak . (See Willows BROOK.) All the generation of the men of war had passed away by the time they reached Zared, fulfilling  Numbers 14:23, that none of them should see the land. From the high ground on the other side of Zared (if Wady Kerak ) a distant view of the promised land and even of Jerusalem might be obtained.

Holman Bible Dictionary [2]

 Numbers 21:12

American Tract Society Bible Dictionary [3]