In 26:27-31 Avimelech and his people come to negotiate with Yitzchak. Yitzchak makes a party for them, they eat and drink. The next day they wake up early and close the deal. Yitzchak sends them home.
Why wait until the next day? They came to do business not to party - they should have negotiated and closed the deal right away. Why wait overnight and have a party first?
On the one hand it shows appropriate behavior. When you have a guest coming to work out a deal, you have to feed them and take care of them. Not just treat it as pure business.
Another point is that it is not good to close the deal too quickly. Let it turn over a bit. Wait overnight and think about things. Do not be too hasty.