Search the Scriptures; for you think that you have eternal life in them: and they are they which testify concerning me. (John 5.39)
John Calvin, commenting on this text, said:
Search the Scriptures. We have said that the statement which Christ formerly made — that he has the Father for a witness in heaven — refers to Moses and the Prophets. Now follows a clearer explanation; for he says that that testimony is to be found in the Scriptures. He again reproves them for their foolish boasting, because, while they acknowledged that they had life in the Scriptures, they perceived nothing in them but the dead letter. For he does not absolutely blame them for seeking life in the Scriptures, since they were given to us for that end and use, but because the Jews thought that the Scriptures gave them life, while they were widely opposed to its natural meaning, and — what is worse — while they quenched the light of life which was contained in them; for how can the Law bestow life without Christ, who alone gives life to it?
Again, we are taught by this passage, that if we wish to obtain the knowledge of Christ, we must seek it from the Scriptures; for they who imagine whatever they choose concerning Christ will ultimately have nothing instead of him but a shadowy phantom. First, then, we ought to believe that Christ cannot be properly known in any other way than from the Scriptures; and if it be so, it follows that we ought to read the Scriptures with the express design of finding Christ in them. Whoever shall turn aside from this object, though he may weary himself throughout his whole life in learning, will never attain the knowledge of the truth; for what wisdom can we have without the wisdom of God? Next, as we are commanded to seek Christ in the Scriptures, so he declares in this passage that our labors shall not be fruitless; for the Father testifies in them concerning his Son in such a manner that He will manifest him to us beyond all doubt. But what hinders the greater part of men from profiting is, that they give to the subject nothing more than a superficial and cursory glance. Yet it requires the utmost attention, and, therefore, Christ enjoins us to search diligently for this hidden treasure.