The Old Testament is highly relevant for the Christian faith and the Christian life. In fact, the Old Testament is essential for the Christian faith and the Christian life. If a person says he or she does not need the Old Testament, or that it is less important and less relevant than the New Testament, that person has a seriously flawed and unchristian view of Scripture.
In 1 Corinthians 10:1-13, the Apostle Paul tells us, among other things, that the Old Testament teaches God’s faithfulness (v13), it teaches the gospel (v4), and it teaches Christian conduct (v6-12). I like how Gordon Wenham cross references 1 Corinthians 10 and Exodus-Leviticus (the wilderness years):
“I want you to know, brethren, that our fathers were all under the cloud (cf. Nu. 9:15-23), and all passed through the sea, and all were baptized into Moses in the cloud and in the sea (cf. Ex. 14:19-31; Nu. 33:8), and all ate the same supernatural food (cf. Ex. 16:4ff; Nu. 11:4ff) and all drank the same supernatural drink. For they drank from the supernatural Rock which followed them, and the Rock was Christ (cf. Ex. 17:1-7; Nu. 20:2-13). Nevertheless with most of them God was not pleased; for they were overthrown in the wilderness (cf. Nu. 14:28-35; 26:63-65).”
“Now these are warnings for us, not to desire evil as they did. Do not be idolaters, as some of them were; as it is written, ‘The people sat down to eat and drink and rose up to dance.’ (Ex. 32:4-6). We must not indulge in immorality as some of them did, and twenty-three thousand fell in a single day (cf. Nu. 25). We must not put the Lord to the test, as some of them did and were destroyed by serpents (cf. Nu. 21:4-9); nor grumble, as some of them did and were destroyed by the Destroyer (cf. Nu. 11:1ff; 14:1ff; 16:42ff).'”
Wenham then comments:
“In this passage Paul describes the experiences of Israel in the wilderness in such a way as to make clear the parallels with the situation at Corinth (Baptism [1 Cor. 1ff]; Manna and Water; The Lord’s Supper [1 Cor. 10:14ff]; Idolatry [1 Cor. 8; 10]; Immorality [1 Cor. 5-7]; Grumbling [1 Cor. 12ff]).”
Since the Apostle Paul viewed the Old Testament this way – as highly applicable to the Christian faith and life – we should do the same. The Old Testament is an essential part of Scripture for us today, as God’s people waiting for the return of Jesus.
(The above quote was from p. 50 of Wenham’s commentary on Numbers – in the TOTC series.)