There's a passage from St. Paul which I found quoted by St. Jerome in his commentary on the Psalms and Origen in his commentary on Genesis:
"And we impart this in words not taught by human wisdom but taught by the Spirit, comparing spiritual things with spiritual things." (1 Corinthians 2:13)
The same passage is translated in very different ways in different translations, but this translation makes the most sense with the way they interpret it (Jerome and Origen seem pretty capable figuring out what it should say). Whenever they cite this passage, they go on to manifest the spiritual meaning of a text by looking at where the same sign is used elsewhere with the same spiritual significance. This is just one of the many ways that Scripture itself teaches us how to read Scripture. St. Augustine in his work On Christian Doctrine and his De Sermone Domini in Monte, goes through the gifts of the Holy Spirit. After the fear of the Lord, he names piety and describes it as the gift by which we receive the Sacred Scripture as truly inspired and submit ourselves in order to learn what the Spirit will teach us through it.
There is a place in one of the prophets that I always found somewhat comical, but it seems to teach that one must understand the literal meaning before the spiritual meaning.
He showed me: behold, the Lord was standing beside a wall built with a plumb line, with a plumb line in his hand. And the Lord said to me, "Amos, what do you see?" And I said, "A plumb line." Then the Lord said, "Behold, I am setting a plumb line in the midst of my people Israel..." (Amos 7:7-8)
Thus the Lord God showed me: behold, a basket of summer fruit. And he said, "Amos, what do you see?" And I said, "A basket of summer fruit." Then the Lord said to me, "The end has come upon my people..." (Amos 8:1-2)
In both of these passages, the Lord shows the prophet Amos some object and asks him what it is. Amos responds with the literal answer right away: "a plumb line" or "a basket of fruit". And only when he has grasped what is manifest, does the Lord then show him what is hidden in it as in a sign. Now to compare spiritual things with spiritual... (I wasn't planning this, but I noticed it)
Moreover, the word of the Lord came to me, saying, "The hands of Zerubbabel have laid the foundation of this house; his hands shall also complete it. Then you will know that the Lord of hosts has sent me to you. For whoever has despised the day of small things shall rejoice, and shall see the plummet (i.e. plumb line) in the hand of Zerubbabel." (Zechariah 4:8-10)
Now it will be plenty of time before I understand the words of the prophets very well, but here we see the image of the plumb line being used, first in Amos and now in Zechariah. Before, the plumb line was in the hand of the Lord and here we see the plumb line in the hand of Zerubbabel. So it seems that a likeness is to be made between them. That Zerubbabel is a sign of Christ is indeed the Lord, the one who laid the foundation and will make things right. Looking around at this entire chapter from Zechariah, it looks like the much of it involves asking the prophet what he sees and him asking what it means, similar to what happened in Amos. When I return to this part of Scripture, I will have to go very slowly and hopefully I will make use of what the Fathers teach about these books.