A basic principle of conversing with non-Christians is “Start where they are.” In starting where they are, you sometimes find they are more familiar with the Old Testament than with the new. So how might you use their familiarity with the OT to engage them in spiritual conversations?
Here are three ways the OT may help you do this:
Transitioning into a presentation of the gospel. Should a spiritually minded non-Christian refer to the Bible, it is helpful to ask what story of the Bible he is most familiar with. There is a good chance he will refer to OT stories he has heard sitting on a Sunday School chair or a grandparent’s lap: Noah and the flood, David and Goliath, Jonah and the whale, Daniel and the lion’s den, the Battle of Jericho, etc.
Upon interacting with them about any of those stories you can then ask, “Has anyone taken the Old Testament and shown you the most important thing of all—how you can know for sure you are going to heaven?”
Moving from a character in the Old Testament to a passage in the New. For any number of reasons reference may be made to the all familiar story of David and Goliath. What an opportunity to show them that though David was a man of many strengths, he was far from perfect. He was a great sinner who received a great forgiveness ( 2 Sam. 11–12; Psalm 51). That leads smoothly into an explanation of how all of us as sinners can also find a great forgiveness. Acts 10:43 explains, “Whoever believes in Him will receive remission of sins.”
Generating spiritual discussion. Often as you speak with unbelievers, a myriad of subjects arise: love and hate, poverty and wealth, loneliness and friendship, peace and war, long lives and early deaths, pride and humility, happiness and sorrow. You might emphasize your enjoyment of reading and then refer to a Proverb of the Old Testament you found interesting.
For example, I often refer to Proverbs 30:7–9, “Two things I request of You (Deprive me not before I die): Remove falsehood and lies far from me; Give me neither poverty nor riches—Feed me with the food allotted to me; Lest I be full and deny You, And say, “Who is the LORD?” Or lest I be poor and steal, And profane the name of my God.”
More than one has responded, “Wow, where did you say that was?” Soon we are talking about how the Bible has helped me in many ways including my eternal destiny.
Just remember when it comes to using the Bible to show where God says first what you are simply repeating, you don’t have one book at your disposal, you have two. One is called the New Testament, the other is called the Old. Use them both!