We believe that Paul is the author of Hebrews.
Paul either wrote/said: 3 how shall we escape if we neglect so great salvation? which began to be spoken through the Lord, and was confirmed for us by those that heard.
Let's look at this verse closer.
1. which began to be spoken through the Lord
2. and was confirmed for us by those that heard
Jesus spoke to His Disciples, they Heard, and then we see they CONFIRMED what Jesus said.
So what did Jesus say to them?
1. 47 and that repentance for the forgiveness of sins should be proclaimed in his name to all nations, beginning from Jerusalem.
2. 16 Whoever believes and is baptized will be saved, but whoever does not believe will be condemned.
3. 38 Whoever believes in me, as the Scripture has said, ‘Out of his heart will flow rivers of living water.’”
39 Now this he said about the Spirit, whom those who believed in him were to receive
So Jesus said to His Disciples 1. Repent, 2. be Baptized, 3. receive the Holy Spirit
How did the Disciples confirm what Jesus said?
38 And Peter said to them, “Repent and be baptized every one of you in the name of Jesus Christ for the forgiveness of your sins, and you will receive the gift of the Holy Spirit.
So Paul, in Hebrews, says LOOK to what Jesus said and what the Disciples confirmed about Salvation.
Peter confirmed Jesus Words:
38 And Peter said to them, “Repent and be baptized every one of you in the name of Jesus Christ for the forgiveness of your sins, and you will receive the gift of the Holy Spirit.