Why were the early believers still going only to Jews years after Pentecost?

Les teaches that the early believers, scattered by the persecution around Stephen, traveled as far as Phenis, Cyprus, and Antioch, preaching the Word—which at that time was only the Old Testament—exclusively to Jews. This was long after Pentecost, about seven years, and they were still adhering to Jesus' commandment in Matthew: 'go not in the way of a Gentile, but go only to the lost sheep of the house of Israel.' Les explains that from Genesis 12 until Acts chapter 9, God was dealing with the nation of Israel, not exclusively but almost. The change of direction would come later, as seen in the Lord's emphasis to Ananias about saving this Jewish zealot, who had been putting Jews to death for embracing Jesus as Messiah.