There are several reasons as to why Nahash may have agreed to their request. To start with, he probably knows something of the history of Israel and how the people of Jabesh-gilead refused to go and help in the war against Benjamin (Judges 21:5–12). The town was subsequently destroyed by the armies of Israel (Judges 21:12). To his mind, it is unlikely that the tribes of Israel would come to help the people of Jabesh-gilead in their time of need, seeing as the people of Jabesh-gilead refused to help them in the past.1 Another reason for his confidence could be the division in Israel as a whole. He did not believe that the tribes would come out together as one in battle and even if they did so, he was confident that he would defeat them.2 Finally, given the distances that messengers had to travel and the fact that they had to do so on foot or horseback, seven days would have been a very short time to muster an army. In light of all these reasons, Nahash was happy to allow messengers to leave the city. Waiting seven days would have been much better than a costly and time-consuming siege.3
3 The elders of Jabesh said to him, “Give us seven days’ respite that we may send messengers through all the territory of Israel. Then, if there is no one to save us, we will give ourselves up to you.”