I have a set of principles I try to use to govern how I do applications in Bible messages. I am sure they are incomplete and imperfect, but I find if I stray too far outside them I end up with applications that are tangential to the passage at best and random at worst.
Here are the first 3
1. There are two main ways to apply Old Testament passages to New Covenant believers:
- In such a way as to show how it speaks about God's big picture, his person, his plans, his salvation and most of all his Christ. I get that from Luke 24 where Jesus says that the whole Bible is about him. I get it from Rom 3:21 which tells us that the Law and the Prophets testify to righteousness in Christ. I get it from 1 Peter 1:10-11 which says that the Prophets main interest was the coming of the Christ. So the applicatory principle is to teach from all the scriptures what they say about God's Crist and his glory
- To give examples and warnings about what is good or bad, pleasing or displeasing to God. I take that from 1 Cor 10:6 & 11. We should never do this before we have done God's big picture, but it really helps in dealing with details of passages. The point of God's big picture is to get to Jesus. The point of examples and warnings is how to be like Jesus. The main application of Joseph and Potiphar's wife isn't fleeing sexual temptation, but it does that quite well too. The main point of David and Goliath isn't being brave and courageous for God, but it does that quite well too
2. Drawing lines of application from Old Covenant passages will always have as its core the centrality of Christ. We do this by seeing how narratives about individuals or individual situations connects to God's bigger narratives about his people and his plans, and by seeing the connection between those mid level narratives and his biggest narratives - salvation history, creation, fall, redemption, consummation, all centring on Christ.
When we have the connection between the individual narrative and Christ we can start to see the connections to us, because we are in Christ. If we don't get the connection to Christ we will be tempted to apply directly to ourselves without asking how Jesus fits into the picture, which is absolutely asking to to get it all wrong. We have to ask "how does this passage relate to Jesus?" before we can ask "how does it relate to people in Jesus?"
3. We have to consider fundamental continuities and discontinuities in scripture. For example, what difference does being in the New Covenant make when applying Old Covenant passages? Do we take them wholesale and apply them without a New Covenant framework? Do we completely ignore them as redundant? We have to figure out what difference Jesus makes to Law passages (for example) if we are not to fall into either error. The chief question to ask is "where is this passage in salvation history compared to where we are in salvation history, and what are teh continuities and discontinuities that have to be born in mind."