Disputations on Holy Scripture by William Whitaker 
After rebuking the false Roman Catholic notion that Scripture cannot be understood by the common man and reinforcing the Reformers insistence that every truth sinners must know to be saved can be gleaned by the simple from reading Scripture, William Whitaker next continued to explain that there are difficult passages in God’s Word. Why? This is his answer …
First, God would have us to be constant in prayer, and hath scattered many obscurities up and down through the scriptures, in order that we should seek his help in interpreting them and discovering their true meaning.
Secondly, he wished thereby to excite our diligence in reading, meditating upon, searching and comparing the scriptures; for, if every thing had been plain, we should have been entirely slothful and negligent.
Thirdly, he designed to prevent our losing interest in them; for we are ready to grow weary of easy things: God, therefore, would have our interest kept up by difficulties.
Fourthly, God willed to have that truth, so sublime, so heavenly, sought and found with so much labor, the more esteemed by us on that account. For we generally despise and contemn [scorn] whatever is easily acquired, near at hand, and costs small or no labor. But these things which we find with great toil and much exertion, those, when once we have found them out, we esteem highly and consider their value proportionally greater.
Fifthly, God wished by this means to subdue our pride and arrogance, and to expose to us our ignorance. We are apt to think too honorably of ourselves, and to rate our genius and acuteness more highly than is fitting, and to promise ourselves too much from our science and knowledge.
Sixthly, God willed that the sacred mysteries of his word should be opened freely to pure and holy minds, not exposed to dogs and swine. Hence those things which are easy to holy persons, appear so many parables to the profane. For the mysteries of scripture are like gems, which only he that knows them values; while the rest, like the cock in Æsop, despise them, and prefer the most worthless objects to what is most beautiful and excellent.
Seventhly, God designed to call off our minds from the pursuit of external things and our daily occupations, and transfer them to the study of the scriptures. Hence it is now necessary to give time to their perusal and study; which we certainly should not bestow upon them, if we found every thing plain and open.
Eighthly, God desired thus to accustom us to a certain internal purity and sanctity of thought and feeling. For they who bring with them profane minds to the reading of scripture, lose their trouble and oil: those only read with advantage, who bring with them pure and holy minds.
Ninthly, God willed that in his church some should be teachers, and some disciples; some more learned, to give instruction; others less skillful, to receive it; so as that the honor of the sacred scriptures and the divinely instituted ministry might, in this manner, be maintained.”
–Disputations on Holy Scripture [1588/1849], by William Whitaker [1547-1595], pp. 365-366. Reprinted by Soli Deo Gloria, 2005.