(Scriptures are quoted from the New International Version Bible.)
We read in the Psalms that "righteousness and justice" are the foundation of God's throne (Psalms 89:14 and 97:2). We know God speaks truth; He is completely impartial; and He does not go back on His word. This is our basis for trusting Him.
Not only is God just, but He is love. (I John 4:8, 16) When God created Adam as a perfect human being, He blessed him and Eve and gave them a beautiful home in Eden. This perfect life could have been theirs forever. In order that Adam and his family would learn to trust and obey God, our Heavenly Father gave Adam only one stipulation, "…You are free to eat from any tree in the garden; but you must not eat from the tree of the knowledge of good and evil, for when you eat of it you will surely die." (Genesis 2:17)
This was a simple, uncomplicated command, but breaking it had grave and far-reaching consequences. Eve was deceived into disobeying God; however, Adam knowingly followed his spouse into disobedience.
God knew Adam was naive, due to his inexperience. And God loved Adam. But God had given His command, and justice must be served. Each person in the human race was now faced with a life of hardship, sorrow, pain, and ultimately eternal death.
The Bible is filled with verses praising God's love and mercy. But if God had ignored his righteous judgment upon Adam in order to show His love and mercy, He would no longer be just. And no one would be able to trust God again.
So God chose a different way to show His mercy. He sent another perfect human being to die in place of Adam, "the man Christ Jesus, who gave himself as a ransom for all." (I Timothy 2:5, 6) Paul says in Romans 3:23-25, "for all have sinned and fall short of the glory of God, and are justified freely by his grace through the redemption that came by Christ Jesus. God presented him as a sacrifice of atonement… He did this to demonstrate his justice." There had to be a satisfaction of justice before God could show His mercy.
The penalty has been harsh, but God is teaching the world the consequences of not trusting and of disobeying Him. Then, when all those ransomed by Jesus Christ come forth in the resurrection (I Corinthians 15:21, 22), they will be ready to walk up the Highway of Holiness to perfect human life, and "sorrow and sighing will flee away." (Isaiah 35:3-10)
This will testify that "mercy triumphs over judgment" (James 2:12, 13).