This is helpful
"The full significance of these words will probably never be understood by Christians until the last day. We have probably a most faint idea of the enormous advantages enjoyed by believers who have lived since Christ came into the world, compared to those of believers who died before Christ was born. The difference between the knowledge of an Old Testament saint and a saint in the apostles' days is far greater than we conceive. It is the difference of twilight and noon-day, of winter and summer, of the mind of a child and the mind of a full-grown man. No doubt the Old Testament saints looked to a coming Savior by faith, and believed in a resurrection and a life to come. But the coming and death of Christ unlocked a hundred Scriptures which before were closed, and cleared up scores of doubtful points which before had never been solved. In short, "the way into the holiest was not made manifest, while the first tabernacle was standing." (Heb. 9:8.) The humblest Christian believer understands things which David and Isaiah could never explain."