In chapter two of his excellent study of Jewish literature from the Second Temple period (586 BC – 135 AD), Larry Helyer discusses the Apocrypha (mostly Tobit and the Additions to the Book of Daniel). In this chapter, Helyer takes some time to explain how a knowledge of the Apocrypha can be a helpful tool for NT studies. In the words of the Belgic Confession, even though the apocryphal books don’t have the “power and efficacy” of the “sacred books” (i.e., the 66 canonical books of Holy Scripture), “the Church may read and take instruction from” them “as far as they agree with the canonical books” (BCF Article 6). Here is Helyer’s list of five ways that the Apocrypha “throws welcome light on the NT writings.”
1) We become more aware of the intense longings for national liberation lying just below the surface of the Gospels. Details recorded in the Gospels are now seen in a new light. We can understand better how Jesus had to refocus the priorities of the disciples (cf. Acts 1:7-8).
2) We can better appreciate the strong antipathy of Jewish-Christian missionaries, like the apostle Paul, toward idolatry and its associated practices. Jewish-Christian missionaries sought to warn and fortify new converts against lapsing back into their former way of life.
3) The early Christians transposed the fact of Jewish exile into a new key. Christians viewed themselves as exiles looking forward to the New Jerusalem (cf. Heb. 13:14, Jas. 1:1, 1 Pet. 1:1). An important aspect of early Christian paraenesis turns on the importance of realizing one’s resident-alien status (Phil. 3:20).
4) Christians, like Jews, faced recurring temptations to assimilate, to compromise with the surrounding culture. Thus, alongside warnings about failing to persevere, NT literature, like the tales from Diaspora, holds out bright hope for the future. Like Tobit 13-14, the book of Revelation radiates with a heavenly vision.
5) Finally, we learn to appreciate how thoroughly Jewish the NT literature really is. Language, diction, imagery, concepts, and ideas are influenced and shaped by the Judaism of the first two pre-Christian centuries and the first Christian century. In short, we recover an essential part of the context within which to read the NT.
This list (which I’ve shortened slightly) is found on page 71 of Exploring Jewish Literature of the Second Temple Period: A Guide for New Testament Students by Larry Helyer.