EXTRA · Parashas Reeh · Third Aliyah · Passuk 13:19
Supplementary classical material for a passuk with no Torah Temimah citation.
When you hearken to the voice of Hashem your God, to keep all His commandments that I command you today, to do what is right in the eyes of Hashem your God.
Classical source: Sifrei Devarim (closing of the ir ha-nidachat section).
English: “When you hearken to the voice of Hashem” — on condition that you hearken; doing what is right in the eyes of Hashem is the condition for the blessing that follows the destruction of the apostate city.
Derash on the conditional close (Sifrei) — the blessing after the herem depends on ongoing obedience.
After the destruction of an apostate city, the promise of mercy and increase is contingent on continued hearkening and doing what is right.