TT #313 · Parashas Shoftim · Seventh Aliyah · Passuk 20:11
And it shall be, if it answers you with peace and opens to you, then all the people found in it shall be tributary to you and shall serve you.
Torah Temimah points to Sifrei Devarim 200.
TT lemma: אִם שָׁלוֹם תַּעַנְךָ.
English: ‘If it answers you with peace and opens to you’ – they accept it.
Derash on the consequence of acceptance (Sifrei) — opening the gates under terms of tribute is sufficient.
If the city accepts the peace offer and opens its gates, its people become tributary and serve; the city is not destroyed.