I think it might be good to first consider the validity of the Old Testament.  We read in 2 Peter 1:21, “For the prophecy came not in old time by the will of man: but holy men of God spake as they were moved by the Holy Ghost.”  This assures us that what is written in the Old Testament was led of God and therefore is pertinent in our lives…even today.  (Also read 2 Timothy 3:16-17).  Here is what the Lord Jesus said about the Old Testament, “Search the scriptures; for in them ye think ye have eternal life: and they are they which testify of me.” (John 5:39).  The Lord was speaking of the Old Testament scriptures because this was the only scriptures that existed at that time.  It shows us that the OT speaks of the Lord Jesus.  Indeed, from Genesis to Malachi, we find the Lord Jesus throughout. 

The Old Testament gives us so much information about the coming Messiah…the Lord Jesus.  It is estimated that the Lord fulfilled about 300 prophesies concerning Himself, therefore showing without a doubt that He is truly the Son of God.  It is through learning about the Lord in these prophesies that we can be assured that He is the very One that God sent to die for our sins.  For example, Isaiah 53:4 prophesied, “Surely he hath borne our griefs, and carried our sorrows: yet we did esteem him stricken, smitten of God, and afflicted.”  We see the fulfillment of that prophesy in Matthew 8:16-17, “When the even was come, they brought unto him many that were possessed with devils: and he cast out the spirits with his word, and healed all that were sick: That it might be fulfilled which was spoken by Esaias the prophet, saying, Himself took our infirmities, and bare our sicknesses.”  In Luke 24:44, we read of the Lord, “And he said unto them, These are the words which I spake unto you, while I was yet with you, that all things must be fulfilled, which were written in the law of Moses, and in the prophets, and in the psalms, concerning me.”  Without the OT, we would have no idea of how to identify the Son of God.

We see that the OT serves as the foundational scripture that reveals to us God’s character, His love for and desire to bless mankind, and His eternal plan of redemption, preparing the way for the New Testament and the coming of Jesus Christ.  It is central to understanding the entirety of the Bible.  The Apostle Paul said in Acts 24:14, “But this I confess unto thee, that after the way which they call heresy, so worship I the God of my fathers, believing all things which are written in the law and in the prophets.”  Paul, in his writings, quoted the OT nearly 200 times.  He spoke of the OT in 1 Corinthians 10:11 where he said, “Now all these things happened unto them for ensamples: and THEY ARE WRITTEN FOR OUR ADMONITION, upon whom the ends of the world are come.”  He expressed quite strongly the need for us to have and learn from the OT.

It is absolutely true that Jesus has fulfilled the whole law as He said in Matthew 5:17, “Think not that I am come to destroy the law, or the prophets: I am not come to destroy, but to fulfil.”  So, believers do not need to try to observe Israel’s former ceremonial and civil laws.  However, it is the giving of the Law, and our complete failure to keep God’s law that shows us our need of a savior.  We read in Galatians 3:24-25, “Wherefore the law was our schoolmaster to bring us unto Christ, that we might be justified by faith. But after that faith is come, we are no longer under a schoolmaster.”  We also read in Romans 3:19, “Now we know that what things soever the law saith, it saith to them who are under the law: that every mouth may be stopped, and all the world may become guilty before God.”  We learn our guilt through the law the Lord gave us.

We cannot over-emphasize the importance of the Old Testament for us today.  The OT makes up ¾ of the inspired Word of God.  The entirety of the scriptures is relevant, powerful, and needed today.  “For the word of God is quick, and powerful, and sharper than any twoedged sword, piercing even to the dividing asunder of soul and spirit, and of the joints and marrow, and is a discerner of the thoughts and intents of the heart.” (Hebrews 4:12)  (CC)  (718.4)