Numbers 32:4

Even the country which the Lord smote before the congregation of Israel, is a land for cattle, and thy servants have cattle:

Cross-reference

Numbers 21:24 Historical context

In Numbers 21:24, the conquest of Sihon is described — the very land struck down by the Lord that is referenced here.

Deuteronomy 2:24–35 Historical context

In Deuteronomy 2:24-35, the defeat of Sihon is retold in detail, providing the full narrative behind the land struck down here.