‘And the seventy two returned with joy, saying, “Lord, even the demons are subject to us in Your name.” '
The disciples returned rejoicing because they had been able successfully to cast out evil spirits. Perhaps they remembered the time when some of them had failed to do so (Luke 9:40). But now success had attended them continually and they were delighted. They had never dreamed that one day they would have this power. Note that they did it through the name of Jesus. It was to His authority that the evil spirits had responded. This clearly struck them more than other miracles of healing, demonstrating the awe in which such spirit possession was held.