Is the Old Testament outdated and obsolete or valuable for Christians to live by?
In many modern religious writings you are likely to encounter considerable prejudice against the Old Testament. That prejudice isn't justified in the light of Jesus Christ's teachings or those of the early Church of God.
While people today neatly partition the Bible into Old and New Testaments, Christ and His disciples did not. "The Scriptures" to them were what people now call the Old Testament writings. When Paul urged Timothy to be "diligent to present yourself approved to God…rightly dividing the word of truth" (2 Timothy 2:15), that "word" was the Old Testament.
Later in the same book, Paul reminded Timothy, "From childhood you have known the Holy Scriptures, which are able to make you wise for salvation through faith which is in Christ Jesus… All Scripture is given by inspiration of God, and is profitable for doctrine, for reproof, for correction, for instruction in righteousness" (2 Timothy 3:15-16). Again, his references to Scripture meant the Old Testament.
Today, we rightly include the New Testament writings in our thoughts, as we read these verses. However, those who reject the actual Scriptures to which Paul referred—the Old Testament—make a serious error.
Again, many religious writers and teachers make that error, seeking to build a theology on the New Testament alone. Their primary motivation seems to be antinomian, that is, a prejudice against the law of God. They usually attempt to minimize what's written in the Old Testament, if not sweep it aside altogether. They mistakenly consider all "Old Testament" laws to be obsolete for Christians except for those validated by New Testament passages. That is not how we approach the unified Word of God. You'll see that United Church of God publications draw upon the Old Testament writings, just as the New Testament writers did throughout all of their books.
How true Christ's words are: "Man shall not live by bread alone, but by every word that proceeds from the mouth of God" (Matthew 4:4).
For more information, please read our booklet The New Covenant: Does It Abolish God's Law?