The question at first is hypothetical , so it matters little wether God did or did not give an unjust command .

So in that sense the question remains relevant : would you obey an unjust command given by God ?

 

Ever read the book of Joshua ?

 

And here is an interesting thing to consider if you are talking Christianity here:  Jesus, the son of God, was quoted in the Bible, but never wrote anything in the Bible.  So even if He was/is the Son of God, every section was written by man based on the history and culture of the time, which happened to include the practice of human sacrifice.  That means that every section of the Bible is subject to man's interpretation of God. 

 

If the Bible were written today, it would still have the same message from God preaching love and peace and how to live a better life, but would sound different because of a different culture and history, yet the truths would remain the same.

 

And if you look at other religions, and boil away the history, the culture, the characters, you will find that all religions teach the same things.  To me, that is proof that there must be a God.

 

In the end, you have to follow your heart and grow your spirituality and in doing so you will get closer to God.