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This is a generalized sketch of the pose of Ananias in The Death of Ananias, one of a series of New Testament subjects painted by Raphael (1483–1520) in 1515 as cartoons for tapestries for the Vatican’s Sistine Chapel (Royal Collection, on permanent loan to the Victoria and Albert Museum, London). The figure is reversed from the original, indicating that Turner copied it from a print. He seems to have made use of it for a figure near the centre of his own essay in the Biblical sublime, The Destruction of Sodom, a painting perhaps shown at his own gallery in 1805 (Tate N00474).1
Martin Butlin and Evelyn Joll, The Paintings of J.M.W. Turner, revised ed., New Haven and London 1984, p.44 no.56, pl.66.