The reason I asked about a Catechism is because it is obviously something other than the Bible. I have been a Christian most of my life, although not always a faithful one. I had my "prodigal son" years, but I have never used anything other than the Bible for spiritual guidance. I would also point out that God has given us "all things that pertain to life and godliness through (by means of) the knowledge of Him who called us by glory and virtue" (2 Peter 1:3). Also, "all scripture is given by inspiration of God and is profitable for doctrine, for reproof, for correction, for instruction in righteousness that the man of God may be complete, thoroughly equipped for every good work" (2 Timothy 3:16, 17).

Therefore, we should "contend earnestly for the faith which was once for all delivered to the saints" (Jude 3). We also do not have the authority/privilege of adding to or taking from Scripture. "For I testify to everyone who hears the words of the prophecy of this book: If anyone adds to these things, God will add to him the plagues that are written in this book; and if anyone takes away from the words of the book of this prophecy, God shall take away his part from the Book of Life, from the holy city, and from the things which are written in this book" (Revelation 22:18, 19).

So, if a Catechism (or any other religious document, for that matter) contains more or something different than Scripture, it contains too much. If it contains less than Scripture it does not contain enough. If it contains the same thing as Scripture, why is it needed?