By "nutshell" verse I am referring to a single verse in the Bible that people like to hold up as a "that sums up that subject" verse. For instance, I have heard a number of people refer to John 3:16 as "the gospel in a nutshell." Indeed, it is a very beautiful and important verse of Scripture, indicating the greatness of God's love in sending His Son to make our salvation possible. However, if John 3:16 was all we needed to know, John 3:16 is all we would have.
Some people act as if 1 John 4:7-8 is all the Bible has to say about the character of God. Indeed, "God is love," but other verses in the Bible have to be considered if we are to have a more accurate picture of God. For instance, Romans 11:22 says, "Behold therefore the goodness and severity of God." Both "sides" of God must be acknowledged and respected.
Once when I was teaching a class on prayer I had a Christian try to make the point that faith was all we needed to be concerned about. Indeed, James 1:6 teaches that faith is an essential ingredient to our prayers, but this is not everything the Bible says about prayer.
Our religious friends and neighbors hold up Paul's answer to the Philippian jailer as the only condition to our salvation: "Believe on the Lord Jesus Christ and thou shalt be saved" (Acts 16:31). When we continue reading the account, we find that Paul and Silas spoke the word of the Lord to him and he was baptized the same hour of the night, in obedience to the Lord's command set forth in Mark 16:16 and Peter's command found in Acts 2:38.
The point I am making in this short article is that we need to beware of those who want to build a doctrine or hang their faith upon a single verse. One of the most basic rules to studying the Bible is that we must read everything the Bible says on a subject before we determine what the Bible teaches on that subject. Don't read too much into those "nutshell" verses.