Albert Barnes Commentary Numbers 21:32

"And Moses sent to spy out Jazer; and they took the towns thereof, and drove out the Amorites that were there." — Numbers 21:32 (ASV)

Jaazer - To be identified probably with the ruins Sir or es-Sir 10 miles north of Heshbon. The occupation of it by the Israelites virtually completed their conquest of the Amorite kingdom; and prepared the way for the pastoral settlements in it which they not long after established (Numbers 32:35).