Old Testament & New Testament

The heresy of Marcion in the early Christian Church still resonates today among some. Marcion claimed the Old Testament was of a different God, therefore we shouldn't use the Old Testament. Today some Christian Churches claim we should use only the New Testament, but what did Christ say? For had ye believed Moses, ye would have believed me: for he wrote of me. But if ye believe not his writings, how shall ye believe my words? John 5:46,47 Search the scriptures; for in them ye think ye have eternal life: and they are they which testify of me. John 5:39 When ye therefore shall see the abomination of desolation, spoken of by Daniel the prophet, stand in the holy place, (whoso readeth, let him understand:) Matthew 24:15 And Paul, as his manner was, went in unto them, and three sabbath days reasoned with them out of the scriptures, Acts 17:2 As a wise author once wrote- "Many who claim to believe and to teach the gospel are in a similar error. They set aside the Old Testament Scriptures of which Christ declared "They are they which testify of me", In rejecting the Old, they virtually reject the New. ..No man can rightly present the law of God without the gospel, or the gospel without the law. The law is the gospel embodied, and the gospel is the law unfolded. The law is the root, the gospel is the fragrant blossom." Christs Object Lessons p.50