Ok here the problem is about interpretation and meaning. Who decide what is merciful? It is subjective and this is the problem. (besides God who is the most merciful of course)

If you are talking about a person who has been crushed by a rock and can not be save and will die of horrible pain in the next 10 minutes then that in ethics could be merciful. We do this with animals who are not moral agents.

But an ISIS supporter could also say that you are a sinner because you are breaking rule X by doing Y (total personal interpretation mind you) and thus need to be saved from this intolerable life you have so you must die (smoked a cigarette under duress?..that s the head gone).

I know it is an asinine analogy but hey that s the problem with subjective issues, they are not objective.

We think about being merciful as doing the right thing to avoid suffering but some people in religion believe that suffering is right to get closer to god. Mother Theresa in Catholicism was known to make her dying patients suffer as she believed it would take them closer to God.

As someone in the medical field I am against any form of direct killing or suicide. I struggle myself with the ethics of assisted suicide. In Islam I believe you are not to help people die but I think a modern interpretation is possible because is to know what God decided someone's death was going to be like. Who are we to say that God may not have wanted us to end the misery of one person.

In essence I don t think you will find an answer and what you believe is the proper thing to do within your conscience and asking God for guidance. If you do something good within your heart then God will know it.

EDIT: Alexinova below made a good post with good quotes and I would agree with him/her.