Why do bad things happen to loved ones?

I was talking with a co-worker and she said her faith has suffered since her sister died of cancer as a young teen. She said, why would God do that to her? I responded that God didn't pick her to have cancer or give her the cancer but rather disease and terrible things happen in this world because of sin. We are all sinful. God didn't give her cancer because she deserved it or was punishing her or her family. Did I tell her the right thing? What is the best way to tell someone why bad things happen to loved ones? Thank you.

I don’t have all the details of your conversation, but it sounds like you were trying to underscore the grace of God when it comes to understanding life’s difficulties and problems.  That is a good subject to underscore.  King David did that when he made this observation about the Lord:  “He does not treat us as our sins deserve or repay us according to our iniquities” (Psalm 103:10).  We are thankful that God does not treat us as our sins deserve, but instead deals graciously and kindly with us.  Sending his Son to be our Savior is proof positive of God’s grace and love and kindness.

While Christians like you and I enjoy peace with God, forgiveness of sins and can look forward to heaven, still we are not exempt from problems and troubles in life.  Jesus, in fact, stated just the opposite.  He told his disciples:  “In this world you will have trouble” (John 16:33).  Jesus’ followers—then and now—are guaranteed troubles because of Satan’s relentless attacks, the unbelieving world’s animosity toward us and the difficulties our own sinful nature may create.  (But read the end of that verse from John’s Gospel.  Jesus went on to say:  “But take heart!  I have overcome the world.”)

God can do one of two things with all the evil coming from those sources:  he can prevent them from entering our lives (Psalm 91:10) or he can allow them to come into our lives for a loving purpose (Romans 8:28).

Your question touches on that last thought:  that a loving God allows troubles into the lives of his children for good reasons.  Here is where we have to bow in humility and awe at the ways and works of God.  We need to acknowledge that his thoughts and ways are not our thoughts and ways (Isaiah 55:8).  We need to confess that God’s wise ways are beyond our understanding (Romans 11:33-36).  We need to trust that God knows at all times what he is doing, and that he is doing what is best for us (Psalm 37:5-6).

In the midst of tragedy Jesus once told a man, “Don’t be afraid; just believe” (Luke 8:50).  That is good instruction for you and me today, because “No one who hopes in you will ever be put to shame” (Psalm 25:3).  When tragedy strikes, we want to keep in mind that what we struggle to comprehend now will be clearer one day (1 Corinthians 13:12).

Finally, a review of the book of Job can be helpful in understanding better the presence of troubles in the life of a child of God.  God bless your witnessing efforts.