ANSWER: Before we delve into this pivotal Biblical event involving Abraham, we need to remember when questioning the motives of God that he is not a human being. Attributing human characteristics to God (or anything other than a human) is called, "anthropomorphizing". When we anthropomorphize God, we commit a grave error of logic. Furthermore, it is an act of folly and a lack of wisdom should we decide that we (God's creation) can "judge" God.
God's love and mercy are by His very nature very different from human "love and mercy" because of the vast differences in potential and power. Since God has the power of resurrection, human death is a vastly different situation for Him than for a human being. A human who takes the life of another, or causes another to lose his life, cannot undo that grievous act but it is as nothing to God to accomplish this act. We live and move and have our being within God. We are His to do with as He wishes, as the ninth chapter of Romans states.
18. So then, He (God) shows mercy to whom He will, and He hardens whom He will . . . Shall the thing that is formed say to the one who formed it, "Why did you make me this way?" (verses 18, 20)
For a human being to make the decision as to whether another lives or dies is an act usurping the power of God and that is why it is such a terrible sin, condemned by all cultures and moral standards other than under special circumstances, i.e., an act of war, or self-preservation or protecting another human being from harm.
Genesis 22 delineates for us the story of Abraham and the commanded sacrifice of son Isaac. As he raised the knife to begin to sacrifice his only child, a voice from heaven cried out for him to stop! He is then informed why he was tested in such a manner.
"Now I know that you honor and obey God, because you have not kept back your only son from him." (Genesis 22:10, 12)
Though God knows "the end from the beginning" (Isaiah 46:10), He always allows human beings to make their own choices. Though God knew what Abraham would likely choose, He still allowed him to make the choice of whether to obey him and offer his son as a sacrifice or to disobey him, showing that he loved his son more. Many years later, the Father would have to make the same choice -- to allow His only son to die so that our sins could be forgiven, or to turn His back on humanity. We praise our heavenly Father for the choice He made.
Abraham did not anthropomorphize God but had faith that whatever happened he would make things right. The father of the faithful knew that our Creator has the life of each of us (including his son) in His hands to do with as He wishes – he also knew that God could bring Isaac back from the dead if He chose to do so.
All of the great blessings that have befallen the descendents of Abraham, including those resulting from the sacrifice of his very distant relative Jesus, were based upon this demonstration of faith with Isaac. We can be proud of our faithful ancestor who, by obeying God rather than attributing human motives to Him, procured all of these great blessings for his descendents and, indeed, for the whole world.