Not often, but on occasion, one might be digging deep into the Old Testament Scriptures to defend their Christian beliefs only to hear, "but that's in the old law...it doesn't matter anymore" (or something kinda like that). So what do you do?
Well, the first thing to recognize is that, while the Old Testament does contain some old laws that we are no longer bound to (like splitting the calf in half, and laying its parts across from one another and waking through them when making an oath), they are STILL the Word of God...they are STILL Scripture. And we also need to be mindful of the fact that , even ignoring the many instances where Jesus and other NT figures quote from the Old, the New Testament does have a bit to say about these.
So, let's observe what the NT Scriptures tell us about the Scriptures themselves. Scripture says, “All Scripture is inspired by God and is useful for teaching, for refutation, for correction, and for training in righteousness” (2Tim 3:16).
Did you catch that? It says "ALL" Scripture. Not just "some", not just "the new"...but "ALL" Scripture is 1)inspired by God, and 2) profitable/useful for...training in righteousness.
Scripture also tells us that the Old Covenant is a foreshadowing of the New...that the Old bears witness to the fullness of the good things to come. “Since the law has only a shadow of the good things to come, and not the very image of them...” (Heb 10:1, NAB). The “Good News Bible” states it: “The Jewish Law is not a full and faithful model of the real things; it is only a faint outline of the good things to come.” And the Douay-Rheims: “For the law, having a shadow of the good things to come, not the very image of the things...”.
We also know that Christ did not abolish the law, but came to fulfill it, “Let your light so shine before men, that they may see your good works and give glory to your Father who is in heaven. Think not that I have come to abolish the law and the prophets; I have come not to abolish them but to fulfill them. For truly, I say to you, till heaven and earth pass away, not an iota, not a dot, will pass from the law until all is accomplished.” (Mt 5:16-18)
So, don't be afraid to discover and discuss what the foreshadowing of God's plan involved, which Christ came not to abolish, but to fulfill and to tell us to let our good work in it shine before all. Let's see how ALL Scriptures can profit us in teaching and training in righteousness.