What is the ruling on swearing an oath to avoid divorce, and does that necessitate expiation, and what is its ruling?

Islam is keen on fostering brotherhood among Muslims and rejecting division among them. It calls for reconciliation between them and permits lying for the sake of reconciliation. The questioner has done well by reconciling between the spouses, but he has done wrong by swearing an oath. If he breaks his oath, he must offer expiation for it: feeding ten poor people, or clothing them, or freeing a slave. If he cannot find any of these, then he must fast for three days.