Because it is the word of God.
The Sacred Scripture
The Bible, also known as Sacred Scripture.
From Genesis to Revelation:Scrip·ture n.1.a. A sacred writing or book. b. A passage from such a writing or book.2. The sacred writings of the Bible. Often used in the plural. Also called Holy Scriptures.3. scripture A statement regarded as authoritative.
The Bible is the sacred text, or Scripture, of Christianity.
bible/ scripture
bible/ scripture
The holy book , or gospel.
The most sacred part is the Torah, which is the first 5 books of the Hebrew Bible.
Your question is too broad. There were rules for determining which books belonged in Sacred Scripture, there are rules as to how to interpret Sacred Scripture. There are rules as to how to nourish your life with Sacred Scripture. There are rules for the inclusion of Sacred Scripture in all of life, and rules for the reading of Sacred Scripture, which ones are you asking about?
The sacred scripture of the Zoroastrians is called the Vesta.
By most the sacred text of Christianity is called the Holy Bible - also referred to as the Scripture. It is a collection of writings inspired by God for mankind - a user's guide if you will. It can be summed up, IMHO, by the term 'love.'
All protestant churches use the Holy Bible as their sacred texts in the same way as the Roiman Catholic Church. The only minor difference is that in the Roman Bible some books are included that are not regarded as worthy of being called 'scripture' in the Protestant Churches. In 'protestant' bibles these books (like the Maccabees, Tobit, baruch etc) are often included in a separate section.