What are the main decision parts of the bible?
The word 'decision' is used only once in the KJV Bible:
Multitudes, multitudes in the valley of decision: for the day of the LORD is near in the valley of decision (Joel3.14)
The 'decision parts' as you mention, come from the preachers rather than from the Bible.
One Scripture that is used here is Revelation 3.20:
Behold, I stand at the door, and knock: if any man hear my voice, and open the door, I will come in to him, and will sup with him, and he with me.
It is said by the preachers that we may make the decision to open the door of our hearts & let Jesus into our hearts. But this is only opened through repentance, as it says in the previous verse, (be zealous therefore, and repent), and this repentance is a gift from the Lord Jesus. (Acts 5.11; 11.18; 2Timothy 2.25)
There are "seven" main parts that make up the Bible. Jesus broke down the "Old Testament" as containing "three" of these seven: The Laws of Moses, the Prophets, and the Psalms. (Luke 24:44) That leaves the New Testament made up of "four" main parts: The Gospels, the Acts of the Apostles, the Letters, and Revelation.
Answer: The Bible does have an important role in our lives, and when we make decisions. The Bible is full of principles, both apparent and hidden. The book of Proverbs can be very useful when trying to make decision: what we should do, and what we should not. So what is the role of the Bible in this case? Counsellor. God Bless. Because it dose