One of the hermeneutical principles of the Reformers was the idea that we are not warranted to universalize Biblical promises without clear revelation to do so.
This is why Reformed theology has always insisted that Jesus’ promise in John 16:13 was specifically for the Apostles as a promise regarding their writing of the New Testament. (1) When one looks at the context, it is very clear that these statements were made specifically for the Apostles.
I could appeal to the general experience of the Church throughout history to back this up. Who else in the two millennia since Christ’s ascension has been able to claim perfect doctrinal accuracy and total recall of Jesus’ teaching? No one but the Apostles can claim this, and they can only claim it in regard to the canonicity of their theopneustic writings.
A more general example is the common appeal to Romans 8:28. We are gravely mistaken when we apply this verse willy-nilly as if everything will always work out fine for everyone. This promise is given specifically for the elect: those called according to God’s purpose. No one else has any business claiming this promise.
Another example is when people try to apply the Old Testament historical narratives to their own personal situations. We’ve all heard the goofy applications: We all have our own personal Goliaths to slay, etc. Pulling those stories out of their redemptive history evacuates them of all their true meaning. Understanding Scripture in any other way than in its redemptive history is to misinterpret it. The stories of Saul, David, Samson, Gideon and Joshua are not given so that we can follow their examples. Christ is our example. Christ is not one among many good characters. He is the only one that matters. All of the Old Testament narratives lead up to Him.
That is why it is wrong for people to try to get guidance from God via a “Gideon’s fleece” experiment. Scripture nowhere tells us that this is how we are to seek the Lord’s guidance. I have know many people who have devised some sort of “Gideon’s fleece” to seek answers to their questions, but I have never known anyone to actually put out a real fleece and test it with dew! Now if they were really sticklers about following Scripture, that’s what they’d have to do.
The story of Gideon shows us how God preserves His covenant people, for His own sake, despite their backslidings, in order to fulfill His ultimate purposes in Christ. Joshua teaches us this same message – not that we are to march around our problems seven times, or some other equally idiotic thing.
The story of Samson is not about how we can make Nazarite vows or grow our hair. It is about God's sovereignty and control over the plight of His covenant people even when their leader are reprobates. Samson was a very sinful man. Whether or not he was a true believer is perhaps debatable, but God overruled his lousy character for His own divine purposes.
(1) Howbeit when he, the Spirit of truth, is come, he will guide you into all truth: for he shall not speak of himself; but whatsoever he shall hear, that shall he speak: and he will shew you things to come.