Palatine Chapel, Palermo, Sicily
The inscription is dixit lamech uxoribus suis occidi virum in vulnus meum et adolescentulum in livorem meum. This is a shortening of Genesis 4:23, "And Lamech said to his wives Ada and Sella: Hear my voice, ye wives of Lamech, hearken to my speech: for I have slain a man to the wounding of myself, and an adolescent to my own bruising" (italics mark what was left out of the inscription).
The mosaic series in the chapel is from the 12th century, but this panel seems to be a product of the restorations done in the 19th. The modeling of the women's faces and Lamech's body is unlike the portraiture in the original mosaics, and the rather crude attempt at vanishing-point perspective in the tiled floor does not seem medieval at all. Also absent is any allusion to medieval exegeses that identified Cain as the slain man and Lamech's own son as the adolescent.
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View other panels in the chapel's Genesis sequence.
Also see this mosaic of Lamech at Monreale Cathedral.
Photographed at the chapel by Richard Stracke, shared under Attribution-NonCommercial-ShareAlike license.