We know the title given to the epistle to the Hebrews is reasonably correct, and Hebrews 1:1-2 provides the internal proof. God sent His prophets to the Hebrew Israelites, including the greatest prophet of all, Jesus Christ. There is no evidence He sent prophets to other nations with any regularity.
However, we must understand that this epistle was not written to Hebrews in general. Like the other epistles, it is directed primarily to Hebrews—Jews or Israelites—who had converted and were fellowshipping in church congregations. Paul, Peter, James, John, Jude, and Matthew were all Israelites, as were others converted through them. Note that other apostles did not send their epistles to the world; they sent them to church of God congregations. Paul explains this spiritually, writing in Romans 2:28-29, “For he is not a Jew who is one outwardly, nor is circumcision that which is outward in the flesh; but he is a Jew who is one inwardly; and circumcision is that of the heart, in the Spirit, not in the letter; whose praise is not from men but from God.” The “Jews” addressed are people with God's Spirit.
The epistle to the Hebrews is inspired, and Christ's words to His church were passed around to all the congregations. This epistle was most certainly not restricted only to Hebrew Christians but was fully intended for all Christians since its instruction is vital to everyone's salvation. Yet, it went first to aid the Hebrews because of what was happening at that time both spiritually and culturally within their nation because of their faith in Jesus as Savior.
The author writes in Hebrews 5:12, “For though by this time you ought to be teachers, you need someone to teach you again the first principles of the oracles of God; and you have come to need milk and not solid food.” This verse indicates that the Hebrew recipients were not young in the faith. Acts 8:1 records what was happening immediately after Stephen's martyrdom: “Now Saul was consenting to his death. At that time a great persecution arose against the church which was at Jerusalem; and they were scattered throughout the regions of Judea and Samaria, except the apostles.” Hebrews 10:32 reminds the epistle's original recipients about their earlier persecutions: “But recall the former days in which, after you were illuminated, you endured a great struggle with sufferings.” We can conclude that the epistle was written to a group of Christians who were not young in the faith.
Hebrews 13:24 adds: “Greet all those who rule over you, and all the saints. Those from Italy greet you,” giving the impression that the congregation may have been relatively large. It also suggests that the epistle probably went first to the congregation in Jerusalem (Acts 11:22) and then copies were made and sent elsewhere.