Matthew Poole and continuators on Numbers 21:27

27 Wherefore they that speak in proverbs , say, Come into Heshbon : let the city of Sihon be built and prepared.

The poets or other ingenious persons, to wit, of the Amorites or Canaanites, who made this following song of triumph over the vanquished Moabites: which is here brought in partly as a proof that this was now Sihons land, and partly as an evidence of the just judgment of God in spoiling the spoilers and subduing those who insulted over their conquered enemies.

These are the words either of Sihon speaking thus to his people, or of the people exhorting one another, to come and possess and repair the city which they had taken.

That which once was the royal city of the King of Moab, but now is the city of Sihon.