How did God's morality not change between OT and NT times? I really have a problem at times explaining to the unbelievers the fact that God wants all people to be saved. The problem is the difference between the morality seen in the OT and the morality seen in the NT. 

In the OT God easily commanded a human to kill 3000 other humans (Exodus 32:27), seemed to be fine to go along with a prophet in his way of proving his genuineness by burning alive 102 other humans, many of which were in fact innocent (2 Kings 1:9-15), and helped some other humans in the way of killing other human beings by stoning them (Joshua 10:11). 

In the NT, however, we see that He forbids humans to perform such acts against other humans (Luke 9:52-56, Matthew 5:39, 44). 

The unbelievers firstly question such a drastic change in His teachings, thus, doubting either about His unchangeable nature or the credibility of Christian faith proclaiming that He is unchangeable, and, secondly, they express a kind of fear ("What if God commands you to kill, will you do that?"). 

How does Christianity deal with such questions? 

Can anyone, please, provide an overview here? (Answers on behalf of only one tradition are also welcome)
The answer is actually pretty straightforward, but it is very difficult for people to accept.

1) God's values, desires, teachings, commandments and interactions with man were exactly the same in the Old Testament as the New Testament.


In the New Testament, we learn that God is love.  Jesus' "new commandment" is that we love one another.  But this really wasn't a "new" idea...
In the Old Testament we have this big, confusing Levitical Law.  But with a little study we can understand it.  One of the commandments is to love God, and another is to love your neighbor.  The rest of the commandments were actually based on these two, and love was the fulfillment of all of them.  Experts in the Old Testament law understood this.  The impossible commandments were intended to hammer it into our thick heads that we are "broken"; we are not loving people!  For instance, adultery is a very unloving action, and if our consciences were working right, that would be obvious.  As it is, we need a commandment to tell us not to treat people like that.
The idea that the Law was "just an Old Testament thing" is false.  The Law that was given in the Old Testament is just as important to understand today as it was back then.  It still teaches us about love, it is still impossible to live up to, we will still be judged by it (unless we are in Christ), and it is still a crucial element in teaching people about God.  (For example, see Matthew 5:17-19.)


2) This is very difficult for people to accept, but we are much more concerned about physical well-being than God is!  From God's perspective, the physical realm is kind of a lost cause.  God wants our focus to be on our spiritual well-being.  Everyone is going to die, because we all have sin!  God can use the timing of our death for His purposes, but death (in some form) is inevitable.  And yet, for some weird reason, when God decides a person's time on this wretched, broken planet is up, we accuse Him of evil for "taking their life."  I assure you - death was never part of God's perfect will.  Man is responsible for death.  But God can use the timing for His loving purposes.

Summary: So, often times we read the stories of the Old Testament and think God is a horrible, ruthless being who could not possibly be in agreement with the teachings of Jesus.  But the reality is, God is love, and everything He does comes from His loving nature.  We are just hopelessly ignorant and corrupt in our understanding of God, so we see the opposite of what is actually true.

Q&amp;A: "What if God commanded you to kill someone?"  If God commands you to do something, it's probably a good idea to do it.  But the real question is, "Would God command you to kill someone?" and the answer is, "No."  We need to discern the voice of God by a proper understanding of Scripture, and it is clear from Scripture that this is not the way Christians are called to walk today.  So why were people in the Old Testament called to do these kinds of things?  Because the things that happened in the Old Testament were visual examples to help us understand spiritual realities.  Now that we have the examples, our job is to use those examples to teach people about spiritual realities.