I. There is no book by the perusal of which the mind is so much strengthened and so much enlarged as it is by the perusal of the Bible. There is nothing so likely to elevate and endow with new vigour our faculties as the bringing them into contact with stupendous truths and the setting them to grasp and measure these truths. If the human mind grows dwarfish and enfeebled, it is ordinarily because left to deal with commonplace facts, and never summoned to the effort of taking the span and altitude of broad and lofty disclosures. The Bible, whilst the only book for the soul, is the best book for the intellect, The sublimity of the topics of which it treats, the dignified simplicity of its manner of handling them, the nobleness of the mysteries which it develops, the illumination which it throws on points the most interesting to those conscious of immortality all these conspire to bring round a result which we insist upon as actual and necessary; namely, that the man who should study the Bible and not be benefited by it spiritually would be benefited by it intellectually.
II. The text ascribes to the Bible precisely that energy for which we have contended. The assertion is that the entrance of God's word gives light, and that it gives also understanding to the simple. We have shown that a mind dark through want of instruction or weak through its powers being naturally poor or long unexercised would become either illuminated or strengthened through acquaintance with the contents of Scripture. But the passage applies with far greater force to the converted than to the unconverted. (1) On conversion there is given to man an increased measure of understanding. In all cases a marked change passes over the human spirit when the heart is renewed by the influences of God's Spirit. The man will have a clearer and less biassed judgment. His views will be wider, his estimates more correct. His understanding, having been exercised on truths the most stupendous, will be more competent for the examination of what is difficult or obscure. His reason, having learned that much lies beyond her province, as well as much within, will give herself to inquiries with greater humility and greater caution, and therefore, almost to a moral certainty, with greater success. (2) Consider certain of the reasons of this fact. (a) The truths which have been commended to the belief are the most sublime and spirit-stirring of all that can engage the attention of mankind. (b) The moral renovation at conversion will be also to a certain extent an intellectual one. Since at the entrance of God's word the man is renewed in holiness, we have a right to expect that he will also be renewed in understanding. (c) The entrance of God's words denotes such an application to the soul of the truths of revelation that they become influential on the life and conversation.
H. Melvill, Sermons,vol. i., p. 147.