Abou Ben Adhem
The main character in the poem is Sufi prophet Abou Ben Adhem. He is a faithful man, and an intelligent one. He is also a righteous man. At the start of the poem, he awakens from a deep peaceful sleep, which suggests that he is not kept awake by worries or concerns about things he might have said or done wrong to others. He is a man at peace with himself. Because of this he is fearless; he is not scared when the angel appears before him, but instead is confident enough to ask questions.
When he hears that his name is not on the list of those who love God, he is unperturbed, which shows that he is a man who genuinely understands his faith, and understands how to live a life that demonstrates his love for God. He knows that to love one's fellow man is to love God, because humans are God's creation.
Abou Ben Adhem was both real life character and mythical figure, in a similar vein to King Arthur or Robin Hood. He was the subject of an epic poem by Rumi which gave Hunt the original inspiration for the poem.
The Angel
Like most angels, the angel who appears to Abou Ben Adhem is an emissary of God, and appears to a human in order to bring a message or to teach something. In this case, the angel is teaching that it is more important to demonstrate love of God than to merely claim in words that one loves God. The angel is patient, and allows Abou Ben Adhem to realize the lesson that is being taught without having to elaborate on it.