By 1779, Benjamin West had conceived his life's "great work," intending to rebuild the Royal Chapel at Windsor Castle as a shrine to Revealed Religion. After sponsoring the elaborate scheme for two decades, George III abruptly canceled it in 1801. Though the overall project was abandoned, many individual paintings, including this nine–foot–long Expulsion, were completed.
The Book of Genesis does not state how the first man and woman were expelled from Eden, but artists usually portray the Archangel Michael as the agent of the Lord's wrath. The sinners wear fur robes because God clothed them in "coats of skins" so that they could stand unashamed in his presence. The serpent, now cursed among creatures, slithers away on its belly to eat dust. The sharp beam of light overhead refers to the "flaming sword" in Genesis.
West's Expulsion contains two motifs not found in Genesis or any traditional pictures of the theme: an eagle swoops upon a helpless bird, and a lion chases frightened horses. In general terms, such beasts of prey imply the destruction of harmony that resulted from Original Sin. Regardless of any further symbolism, West's artistic treatment foretells the new romantic style with its theatrical gestures, rich paint textures, and clashes of blinding light and shadowy darkness.
More information on this painting can be found in the Gallery publication American Paintings of the Eighteenth Century, pages 296-297, which is available as a free PDF at https://www.nga.gov/content/dam/ngaweb/research/publications/pdfs/american-paintings-18th-century.pdf