...We just discussed this in Sunday school, the Old Testament (OT) and the New Testament (NT). ...The entire Bible is our guidebook for life. We find this in 2 Timothy 3:16-17:
...16 All Scripture is God-breathed and is useful for teaching, rebuking, correcting and training in righteousness,
...17 so that the man of God may be thoroughly equipped for every good work.
...Christ is the end of the law for righteousness to everyone who believes. The OT contained types or foreshadowings of things to come. The OT had many laws to follow for the nation Israel, and we are not subject to them today under the New Covenant.
...For believers, Christ paid for all our sins, and now we live by the law of love - Matthew 22:37-40 says this:
...37 Jesus replied, “‘You must love the Lord your God with all your heart, all your soul, and all your mind.’
...38 This is the first and greatest commandment.
...39 A second is equally important: ‘Love your neighbor as yourself.’
...40 The entire law and all the demands of the prophets are based on these two commandments.”
...And in Romans 13 we find this:
...8 Owe nothing to anyone—except for your obligation to love one another. If you love your neighbor, you will fulfill the requirements of God’s law.
...We are not to discard the Old Testament, though. There are many principles and lessons to learn there, and that is where you will learn what God says about what is right and wrong.
...In Romans 15:4 we read, "For whatever was written in earlier times was written for our instruction, that through perseverance and the encourage of the Scriptures we might have hope."
...We follow God's leading today by being filled (controlled) by the Holy Spirit, by reading God's word, and listening to godly counsel.
...The only other thing I can think to say is this: To understand the Scriptures, you must be a Christian. See 1 Corinthians 2:14
...14 But a natural man does not accept the things of the Spirit of God, for they are foolishness to him; and he cannot understand them, because they are spiritually appraised.