In modern biblical scholarship, a lot of energy is spent trying to understand author intention and historical context for each and every bit of Scripture. Read any introduction to any book of Scripture (particularly from the OT) in an annotated edition of the Bible, and therein much ink is spilled speaking of when, where and who wrote various verses, let alone entire chapters and books.
I don’t point this out to complain — there is much to learn about Scripture from such an approach. Indeed, studying the Jewish liturgical rites of the Temple at the time of Christ add an incredible depth to our understanding of the Gospel According to John, for example. I bring this up to contrast it to the exegetical approach of the Fathers of the Church, particularly those of the fourth century.
Rather than dissecting Scripture into various pieces and parts to be studied within their own context, the Fathers tend to look at the Bible as a whole. They have no qualms about juxtaposing verses from very different parts of Scripture in order to make their arguments over the nature of God. It is a methodology that might take some getting used to, but by the very fact that it is extensively used by the Fathers, it is something we need to acknowledge.
For example, in the first chapter of the first book of his treatise On the Holy Spirit, St. Ambrose juxtaposes three verses in order to speak about the divinity of the Holy Spirit. They are Psalm 118 (119):91
They continue this day according to Your ordinances, for all are Your servants.
1 Corinthians 2:10
God has revealed them to us through His Spirit. For the Spirit searches all things, yes, the deep things of God.
and John 15:26
When the Paraclete comes, whom I shall send to you from the Father, the Spirit of truth who proceeds from the Father, He will testify of Me.
His argument goes something like this: If the Holy Spirit is not God, than He must be a servant of God, according to Psalm 118(119):91. When held up to 1 Corinthians 2:10 and John 15:26, however, the Holy Spirit must be God, or we must think very little of God the Father. How is it that a mere servant or a mere creature can search out the deep things of God? Surely only God can do that. How is it possible for a servant or a mere creature to not only proceed from the Father, but be intimate enough with the Son to be witness to the “full expression of the Divine Majesty” (as St. Ambrose describes it)?
The only way that all three of these verses can be true is if the Holy Spirit is God.
Despite there being three different authors, three different genres, three different contexts, all three verses speak to each other. There is an internal logic that can be discerned throughout Scripture about God and His creation. Thus, if something can be stated in the Psalms about God and His creation, it must hold true in the Gospels and the Epistles and vice versa.
This is the exegetical style of the Fathers. I expect that we shall see more of it as we move forward in the treatise of St. Ambrose On the Holy Spirit.