Luke 4:25 - 27
ESV - 25 But in truth, I tell you, there were many widows in Israel in the days of Elijah, when the heavens were shut up three years and six months, and a great famine came over all the land. 26 And Elijah was sent to none of them but only to Zarephath, in the land of Sidon, to a woman who was a widow.
For follow-up discussion and general commentary on the topic. Comments are sorted chronologically.
A brief point of trivia: both Naaman and the widow were gentiles.
One point that can be taken from this passage is that just as it was not the Israelites who were healed in these instances, rather gentiles that obeyed the prophets, so spiritual healing (salvation) is not based on the physical 'people of God' but all those who have faith in Christ. The true Kingdom of God is spiritual, not ethnic.
The Jews believed that salvation would belong only to them, because they were the chosen people of God. Yet they did not always obey God, or even recognize the Messiah when He came. They were more willing to serve Rome than to accept Jesus (John 19:15).
Yet Jesus came to the outcast, the poor, the sinners, the humble. As Jesus said, "It is not the healthy who need a doctor, but the sick. I have not come to call the righteous, but sinners." Mark 2:17
This is a very good point, I know that there are reports of miraculous healing performed by missionaries among the unreached, pagan people; as this is necessary to cause the population to believe in God and His compassionate redeeming grace; His power of regeneration, resurrection salvation from death. Also as you said obeying God is the most important thing as mentioned in 1 Samuel 15:22. Naaman was healed after he obeyed and went to wash 7 times as he was skeptical at first.
I think that God is interested in a vessel that He can use to demonstrate His power,Sovereignty,Love and compassion for humanity,and wherever that vessel be found,whether in the east or west,north or south,the Lord will use that vessel
But in a great house there are not only vessels of gold and of silver, but also of wood and of earth; and some to honour, and some to dishonour. If a man therefore purge himself from these, he shall be a vessel unto honour, sanctified, and meet for the master's use, and prepared unto every good work. (2 Timothy 2:20-21 KJV)