A. Because it is inspired of God.
       1 Peter. 1:10-12
       2 Peter 1:19-21 - Just as the New Testament writers spoke by inspiration, so did the prophets.
        2 Timothy 3:16-17 - all scripture inspired of God is profitable...
       Jesus often referred to it as inspired - Luke.24:44; Matthew 4:4,7, 10.
    If there we no other reason to study the Old Testament, this one would  be sufficient. If it comes from God it serves a purpose and it is to be respected and considered, as such.

    B. We Are Told To Study It
        1 Cor. 10:11 - they happened as an example...
        Gal. 3:24 - It was a schoolmaster to bring us to Christ
        Rom.15:4 - Written for our learning...
        2 Pet. 2:6 - making them an example

    C It Is Continually Referred To In The New Testament
        1 Cor.10:1-10 - reference to Israel while in the wilderness
        Heb. 11:1-40 - faith, based upon the example of the of the Old Testament
        Jas. 5:17-18 - Elijah a man of prayer
        Jas. 5:10-11 - the patience of Job

    D. It Confirms Our Faith in the New Law
        Prophecies - even the agnostic historian (if he is honest) will confirm that the Septuagint (Old Law translated into Greek) was written before Christ was upon this earth. Yet that which is said about Jesus (which is also confirmed) is often prophesied of in the Old Testament.  The prophecies would be meaningless without the Old Testament. 
        There are literally dozens of prophecies about Christ and His church foretold in the Old Testament. Many who shun the Old Law have no problem accepting the Christ that it forth tells about. We need both.

    E. It helps us to better understand the New Testament.
     There are major parts, even books that CANNOT be understood without the Old Law - consider Romans, Galatians & Hebrews.
          Many concepts of the new law are based upon the old law   I.E. - Type-Anti-type relationships.
     2 Peter 2:5-9 - the ancient world & Sodom & Gomorrah were destroyed because of their disobedience, thus we see an example that God can deliver the righteous (Noah & Lot), AND reserve under judgment the
        wicked.
        Hebrews 10:1 - the law having a shadow of good things to come
        Hebrews 9:23-24 - copies of the true.  (9:9) - symbolic...
        1 Peter 3:20-21 - there is also an antitype which now saves us...
            (KJV- the like figure whereunto baptism doth now save us.)
      Galatians 4:21-31 - Hagar (Ishmael) & Sarah (Isaac) - the old law to be taken out of the way and replaced with a new law. Note v.24 - which things are symbolic.

    F. It helps us better understand God
      Romans11:22 tells us to consider the goodness and severity of God. In the Old Testament we learn clearly about His character. One good example of it would be Nahum 1:2-7 where we learn (just last week) of His goodness, jealousy, omnipotence, omnipresence, etc.

II. Helpful Hints In Studying The Old Testament

    A. Remember that the events of the Old Testament are real - a real history about a real people (that still exist today).
       They are confirmed in history books, including some of the kings of Israel & Judah. It is incomplete in the eyes of the world, but it is complete in telling us everything we need to know. Its theme is How can man be redeemed from his sin?
       Every civilization records a great flood. Archaeology constantly confirming the history of the O.T.

    B. There are 5 key passages - all the O.T. linked around these 5 texts (and  ideas)
        Genesis 3 - The fall of man, the first messianic prophecy
        Genesis 12 - The promise to Abraham
        Exodus 20-24 - The giving of the Law of Moses
        2 Samuel 7 - The promise to David
        Jeremiah 31:31 - The promise of a new covenant

    C. Names have meanings -
        Whenever God gives a name, remember the meaning and it will help you remember the person. e.g. - Abram - Exalted father.   

        Abraham - father of many nations.
        Ishmael - God hears -(answer to Hagar’s prayer). Israel - "To strive with God"  Gen.32:28
        Jacob - supplanter, Joshua - savior, The prophets - Nehemiah - Comfort of Jehovah.

    D. Natural laws stay the same
        Gen. 1:11, etc. - according to its kind
        Wisdom of Solomon - Proverbs, Ecclesiastes - very practical, even today
        Laws of science - Sanitary laws to the Jews -clean & unclean foods & animals.
        Circumcision the 8th day.- best time. Before - blood does not clot properly.  After more painful.
        Ground to rest every seven years. I.E. Crop rotation, etc.
        These "hints" can help you to better understand the Old Law as you study it.

Yes it is true that we are no longer under the Old Law. Col. 2:14 tells us it was taken out of the way. Heb. 10:1-4 reveals the flaws of the law, why it needed to be replaced, what replaced it, etc. But such would be meaningless if we did not know what He was talking about. Nor could we properly understand the intended messages that we are COMMANDED to follow based upon the examples of the Old Testament. May we give the proper respect to all of God’s word. Using it as God intended it to be used.

ALL SCRIPTURE INSPIRED OF GOD IS PROFITABLE...