Readers of the Bible are often aware of when someone is speaking as the context lends itself to it. This is especially true regarding the words of Jesus when we read them in Bibles containing red print. However, we often gloss over passages that contain quotes.
In the Old Testament, it was common for the prophets to quote God. As a matter of fact, it was assumed that true prophets were speaking on his behalf. However, in the New Testament, we see the writers—especially well-educated ones—quoting other sources.
Here are a few examples from Paul's writings:
Romans 2:6 (NIV84)
God "will give to each person according to what he has done."
Acts 17:26-28 (ESV)
And he made from one man every nation of mankind to live on all the face of the earth, having determined allotted periods and the boundaries of their dwelling place, that they should seek God, and perhaps feel their way toward him and find him. Yet he is actually not far from each one of us, for "In him we live and move and have our being"; as even some of your own poets have said, "For we are indeed his offspring."
1 Corinthians 5:32 (ESV)
What do I gain if, humanly speaking, I fought with beasts at Ephesus? If the dead are not raised, "Let us eat and drink, for tomorrow we die."
1 Corinthians 5:33 (ESV)
Do not be deceived: "Bad company ruins good morals."
Titus 1:12-13 (ESV)
One of the Cretans, a prophet of their own, said, "Cretans are always liars, evil beasts, lazy gluttons." This testimony is true. Therefore rebuke them sharply, that they may be sound in the faith, not devoting themselves to Jewish myths and the commands of people who turn away from the truth.
Quoted passages should not be glossed over so quickly. We shouldn't merely assume they are there for flavor or character of speech. In the cases above, Paul was extremely educated, and he had a large number of sources at this disposal. Why did he choose these particular ones, and why did he use them in these instances? What can we glean from his message and use of these extrabiblical sources? Furthermore, how do we even start to perform adequate discovery?
Before we begin the actual interpretation and any resulting, personal application, let's consider how to approach these sources.
Be aware
As stated above, slow down and do not gloss over these references. They were apparently important enough for the speaker or writer to reference them. Additionally, we can assume they were important if they were included in the Bible. Therefore, begin to notice when and how they are used.
Compare translations
You'll find that some quotes, such as the one in Romans 2:6, isn't present in all translations (it appears as a standard part of the statement in the ESV). Why is that? Why is the quote present in some but not in others? Is this a result of what's known as oral tradition—the formation of the Bible texts as information was passed by word of mouth and captured by various writers over time? Take note of the differences and, if you can, seek to understand why.
Explore other sources
While previously it was very difficult to search for references, we are now in the age of information technology, and references are literally at our fingertips. Use the Internet to search for the earliest references to these quotes. In doing so, you may uncover additional context and meaning to the quotes that would have only made sense to 1st-century hearers/readers. For example, the phrase "follow me" meant something entirely different in the first century compared to today (Facebook didn't exist yet).
Don't be afraid
There is an unwarranted fear among traditional, conservative believers today that other sources should not be used to validate the Bible. For them, the Bible is the only source of truth, and everything else should be disregarded. But, this belief is often the result of fear or lack of knowledge (which Paul tells us to rid ourselves of both). Though the Bible is true (the only source of absolute truth, and it is inerrant and infallible), it doesn't make every other book a lie, and there are plenty of sources that confirm and support the message of the Bible, even secular ones. We can leverage these sources to affirm our message and relate to others as we share the Gospel.
With the above said, let's now turn our attention to the texts themselves and consider a few of them.
Acts 17:28
When Paul states, "For we are indeed his offspring," he is quoting an poem that Aratus, a fellow Greek, wrote regarding astronomy. Aratus predated Paul by approximately three centuries, but Paul references Aratus to describe our relationship to the Father. In a very pantheistic society, Paul focuses his listeners on the simple, yet profound, message that we are God's children. This concept would have been quite foreign but welcomed by his hearers.
1 Corinthians 15:32
Paul is quoting the prophet Isaiah (22:13) in creating an opposite of extremes. In drawing attention to Israel's complacent and laissez faire attitude that Isaiah condemned, Paul crafts a hyperbole. He essentially asks, if the Gospel is a lie, then why bother demonstrating any effort. Instead, have fun, enjoy life, and die on a full stomach.
1 Corinthians 15:33
"Bad company ruins good morals" is a phrase found in the play Thais, which was written by Menander, a 4th-3rd century B.C. poet. To make a (very) long story short, Thais was a hetaera, or a well-educated prostitute who was an artist, entertainer, and conversationalist, along with providing sexual services for the elite. In particular, Thais was the wife of Ptolemy, but could have also been a lover of Alexander the Great. The story goes that, while at a drunken party, Thais delivers a speech that arouses Alexander's court and insights them to take revenge on the Persians for their destruction of Athens under the leadership of Xerxes.
In context, given the adjoining verses (e.g., "eat and drink", "drunken stupor"), Paul is again depicting two extreme ends. On the one hand, if Christ and the resurrection is real, then the audience should cease their sinful acts. In neither is true, then Paul argues there is no benefit to restraining. Paul, once again, engages in hyperbolic argument to make his case.
As you can see from just three examples, there is quite a bit of hidden meaning behind that which seems so obvious at a simple glance. While the quotes alone make sense in context, understanding the source of the quotes paints a much richer picture and draws a incredibly deeper meaning. Don't be too quick; don't gloss over the quotes. Take the time to understand them. The quotes are there for a reason.