WCF and Biblical Theology
The covenant theology of the WCF is developed... around a functional, though not scientifically precise, concept of biblical theology. The covenantal perspective highlights the pre-/postlapsarian distinction and so highlights the sinfulness of sin and the amazing character of God's free grace. The fact that covenant theology can have such an indispensable place within a confession that proceeds on a loci methodology well demonstrates that biblical theology and systematic theology, far from being antithetical, are in fact complementary!
David McWilliams , The Covenant Theology of the Westminster Confession of Faith and Recent Criticism, Westminster Theological Journal, 53 (1991), 123