A fabel (paraphrased by me)

There once was a man who was standing in the snow next to a river. The man saw a snake, half frozen and near death, lying in the water. He took the snake home and cared for it, fed it, and nursed it back to health. The snake started to recover. The man continued to care for the snake for an entire week. At the end of the week, the man picked up the snake the snake bit him. As the man lay dying he asked "I fed you and cared for you after saving you from certain death. Why did you bite me?" The snake looked at the man and said "You knew what I was before you picked me up."