Is it permissible to grant a truce (aman) to the inhabitants of a besieged fort if they promise to open it?

Primary text

It is permissible for Muslims who have besieged a fort to grant a truce (aman) to a man who calls out to them asking for it in exchange for opening the fort. This occurred when Ziyad ibn Labid besieged Najir, and Al-Ash'ath ibn Qays requested a truce for ten men in exchange for opening the fort, and they complied.