They Always say Goodbye before they fly away

The church was filled with people, yet as the minister gave his sermon, only a few truly listened. Had they heard the lesson, they would have learned that we need to help other people because we never know if the person we might be helping is actually an angel in disguise.
"Angels?" said one little boy to his sister, "How can you know if someone is really an angel?" His sister thought for a while, then replied, "Because they always say goodbye before they fly away."
As the boy left the church with his family, his sister's words stayed with him - they always say goodbye before they fly away. Over the next few months, the boy didn't forget, and one day he saw a man in the street, dressed in rags and obviously in need of food. He tossed the man a buck and bought him some food - something he always did now when he saw someone who needed such help. As he turned to walk home, the man said, "Goodbye."
The boy turned quickly back, eager to see if the man would fly away. But he didn't. The man stayed exactly where he was, and the boy walked away, disappointed. Had he continued to watch, for just a little longer, the boy would have seen the man's rags turn linen white as he flew up into the air.
More years passed. However, the boy didn't forget. A teenager now, he saw a lady struggling with a heavy bag. She was trying to cross the street, right in the path of a speeding car.
The boy saw what was about to happen, and he ran up to her and pushed her out of the car's path. The lady was safe, but unfortunately, the boy was not - he'd taken the full impact of the collision.
As he was breathing his last breaths, he saw angels and noticed that each one was familiar. One was the lady he had just saved. Another was the homeless man in rags. There were many more, and each revealed themself to be a person the boy had helped over the years. They smiled at him and said, "Hello." The boy had helped so many people. Not all were angels, but many were.
I wonder, how many angels have you helped, thinking it was just a person in need?