In the preface to the 1539 Edition of the Institutes, Calvin explains the purpose of the Institutes and in doing so offers good counsel regarding the need for theology in reading Scripture well:
It has been my purpose in this labor to prepare and instruct candidates in sacred theology for the reading of the divine Word, in order that they may be able both to have easy access to it and advance in it without stumbling. For I believe I have so embraced the sum of religion in all its parts, and have arranged it in such an order, that if anyone rightly grasps it, it will not be difficult for him to determine what he ought especially to seek in Scripture, and to what end he ought to relate its contents.
Calvin sees his doctrinal work as the handmaid to a faithful and fruitful reading of the Bible. According to Calvin, good theology does not obscure the plain meaning of Scripture, but may rather illuminate it. Orthodox doctrine may open one’s eyes to see what might otherwise have been missed.
The next time I encounter a difficult passage, maybe I’ll consult a systematic theology.