St. Joachim
Mid-12th century
Mosaic
Co-Cathedral of St. Mary of the Admiral ("The Martorana")
Palermo, Sicily
The Greek words to the figure's left and right, Ο ΑΓΙΟS ΗωΑΚΗΜ, identify him as "Saint Joachim." According to one source on the internet, "Open palms held at chest height have two meanings. The first one is a prayer to God; the second is the acceptance of grace."1
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Photographed at the Martorana by Richard Stracke, shared under Attribution-NonCommercial-ShareAlike license.
1 The source is a commercial site, "Russian Icons and Antiques," https://russianicon.com/hand-gestures-orthodox-icons/
I found it on May 18, 2019. The information may or may not be trustworthy.