[How Does the Immutability of God Affect Us? by Steve Ham] "The Bible is given to us by One who claims to be “unchangeable” (Malachi 3:6). This really is what immutability means (i.e., God does not change). If the Bible is the inspired Word of God (and, therefore, the authority in all that is within it), would it truly be trustworthy if God’s character was changeable and, as a result, unreliable? Yet, the Bible confirms that God’s character is immutable.

We see this consistency in the ordinances we live within. Jeremiah 33:25 states that God appointed these very ordinances, and we know they are ordinances that do not change because they are constant (like the laws of logic, mathematics, physics, chemistry, etc.). Without these constant laws ordained by a self-existent, immutable God, we would not be able to reason nor act.

Immutability is one of the amazing things about God’s character that is consistently expressed through the whole of Scripture; God’s character traits interweave without contradiction throughout the Scriptures in a perfect harmony. Take for instance the work of Christ on the cross. In one act, we see God’s perfect character in justice and wrath on sin being poured out at the same time as His mercy, grace, and love. Sin is dealt with through justice, and mercy is delivered through grace. Coupled with the fact that God is the everlasting God, we know and rely on His eternal justice upon sin as much as His everlasting grace and mercy for every believer.

So when Malachi tells us that it is because of God’s immutability that we are not consumed, we see this consistency in His character. A biblical understanding of God’s unchangeable character reconciles His justice upon sin and way of salvation for sinners, which will not change. God being immutable and keeping his promises is the reason that the message of Jesus Christ is even available to us and that we are not consumed. These are the interwoven, unchangeable attributes of a consistent, constant authority. The Scripture also confirms this by telling us He is faithful, which is expected from an unchangeable God." Full text:  How Does the Immutability of God Affect Us? by Steve Ham http://www.answersingenesis.org/articles/2010/05/13/immutability-god

Biblical Authority Pt III: How Does the Immutability of God Affect Us?