However, when we come to the internal, Biblical evidence, we find the strongest opponents of Pauline authorship rise up. Though history has authority in some sense, councils do err and church history is full of mistakes to prove it. Thus it is important to also consider what evidence the Bible puts forth concerning the author of Hebrews. There are at least three internal evidences for Pauline authorship:
The first internal evidence for Pauline authorship is found in the last verse of Hebrews. Hebrews 13:23-25 reads: “You should know that our brother Timothy has been released, with whom I shall see you if he comes soon. Greet all your leaders and all the saints. Those who come from Italy send you greetings. Grace be with all of you.”[1] Three points emerge from this passage: a) Italy is the place of origin for this letter. If the date of this letter is between 62 and 65AD, as most scholars seem to agree, then this would be during the time that Paul is imprisoned in Rome. B) We read the name Timothy. We know that Timothy was a close companion of Paul. In fact, Paul called Timothy a son. Timothy could have written down Paul’s dictation of the letter to the Hebrews. C) Paul closes his epistle with the words: “Grace be with you all.” In the words of one scholar, this is Paul’s signature trademark. No one else ever closes their writing in this manner.
The second internal evidence is that Paul has the strongest doctrine of justification by faith in his writings. He deals 
with this doctrine extensively in Romans and Galatians. He alludes to Old Testament stories to make his point. He talks about Abraham and Moses as a picture of true faith. In fact, Paul is the only one that ever quotes Habakkuk in the famous line: “The Just shall live by faith.” In Hebrews 10, the writer echoes the same passage in Habakkuk. If you study Hebrews alongside Romans and Galatians you will find a host of other similar theological topics discussed, particularly the subject of faith.[2]
Finally, we have the well-known passage from II Peter 3:14-15: “And count the patience of our Lord as salvation, just as our beloved brother Paul also wrote to you according to the wisdom given him, 16 as he does in all his letters when he speaks in them of these matters. There are some things in them that are hard to understand, which the ignorant and unstable twist to their own destruction, as they do the other Scriptures.” There are three things to observe from this passage: a) Peter says that some of Paul’s writings are difficult to understand. Anyone who has studied Hebrews knows that this description fits the bill. If translating Hebrews in Greek is an excruciating experience, then understanding the theology of Hebrews seems even more complex. In fact, in Hebrews 5:11 the author says that some things are hard to explain to the readers. The audience in Hebrews is a Jewish Christian audience who are not very mature in their faith, who run the risk of falling away; so the writer says that some things he has to say will be hard for them to understand in light of their background, but he says, they need to grow up and understand them. I believe Peter has Hebrews in mind. b) Another point is that Peter says that the ignorant twist Paul’s words to their own destruction. This also fits with Hebrews. Only in Hebrews does the author give a stern warning to those who are twisting the Word and who are tempted to abandon the faith and go back to the Old Creation of sacrifices and blood. C) Finally, here is the strongest argument in my opinion. II Peter 3:1 says that Peter is writing to the saved Jews. Then in verse 15 of the same chapter, Peter says that Paul also wrote to them according to the wisdom given. A.W. Pink concludes by saying that “if the epistle to the Hebrews is not that writing, where is it?”[3]
[1] Quotation from the English Standard Bible.
[2] Consider Hebrews 11, as an example.
[3] A.W.Pink, An Exposition of Hebrews, 18. Also, Dr. Robert Reymond says that the internal evidence also supports the legitimacy of holding that Paul could have been the author.
