Why does the book of Hebrews use so many Old Testament references?
The book of Hebrews draws heavily on the Old Testament because its author wrote primarily to Jewish believers, so he used Israel's history, Psalms, and wilderness experiences to make his points. Quoting familiar Scriptures and events connected the argument to his audience's heritage and warned them against unbelief.
Les explains that when Paul wrote the book of Hebrews, he was writing primarily, not exclusively, to Jewish believers. Consequently, he used many Old Testament contacts and experiences to make his point. For example, in Hebrews chapter 3, verse 7, Paul quotes from the book of Psalms: “Today, if you will hear his voice, harden not your hearts, as in the provocation, as in the day of temptation in the wilderness.” Les connects this to the forty-year wilderness experience that followed their rejection of going in at Kadesh Barnea, and to God being grieved with that generation that said they would lose their women and children. The Old Testament references fit Jewish believers and served as a warning.