If you believe Paul wrote the Hebrew Christians then Paul wrote to all Christians:
Why don't you take this opportunity to educate yourself by reading the whole chapter ___ learn.
"Take this opportunity to educate yourself" on how we can know that Paul did NOT write Hebrews. Here's one of the reasons: every epistle Paul wrote begins with the salutation of "Paul".
2 Thessalonians 3:17
The salutation of Paul with mine own hand, which is the token in every epistle: so I write.
See for yourself:
Romans 1:1
Paul, a servant of Jesus Christ, called to be an apostle, separated unto the gospel of God,
1 Corinthians 1:1
Paul called to be an apostle of Jesus Christ through the will of God, and Sosthenes our brother,
2 Corinthians 1:1
Paul, an apostle of Jesus Christ by the will of God, and Timothy our brother, unto the church of God which is at Corinth, with all the saints which are in all Achaia:
Galatians 1:1
Paul, an apostle, (not of men, neither by man, but by Jesus Christ, and God the Father, who raised him from the dead
Ephesians 1:1
Paul, an apostle of Jesus Christ by the will of God, to the saints which are at Ephesus, and to the faithful in Christ Jesus:
Philippians 1:1
Paul and Timotheus, the servants of Jesus Christ, to all the saints in Christ Jesus which are at Philippi, with the bishops and deacons:
Colossians 1:1
Paul, an apostle of Jesus Christ by the will of God, and Timotheus our brother,
1 Thessalonians 1:1
Paul, and Silvanus, and Timotheus, unto the church of the Thessalonians which is in God the Father and in the Lord Jesus Christ: Grace be unto you, and peace, from God our Father, and the Lord Jesus Christ.
2 Thessalonians 1:1
Paul, and Silvanus, and Timotheus, unto the church of the Thessalonians in God our Father and the Lord Jesus Christ:
1 Timothy 1:1
Paul, an apostle of Jesus Christ by the commandment of God our Saviour, and Lord Jesus Christ, which is our hope;
2 Timothy 1:1
Paul, an apostle of Jesus Christ by the will of God, according to the promise of life which is in Christ Jesus,
Titus 1:1
Paul, a servant of God, and an apostle of Jesus Christ, according to the faith of God's elect, and the acknowledging of the truth which is after godliness;
Philemon 1:1
Paul, a prisoner of Jesus Christ, and Timothy our brother, unto Philemon our dearly beloved, and fellowlabourer,
Hebrews does not!
Hebrews 1:1
God, who at sundry times and in divers manners spake in time past unto the fathers by the prophets,