The Iranians President probably knows that how easy it is to trigger a war, and how difficult it is to stop one. Especially if the initial attack is a bloody one.
But as a gesture of good will, if the jihadis were to return all the 97 hostages alive and well to return to Israel, then it would definitely be a positive step. But as with nearly all cases of kidnapping, if the captives are murdered by their kidnappers, then the cold hand of law and order, shows little grace towards the criminals.