A note of ambiguity or unease often gives a piquant quality to German adaptations of the Renaissance ideal. Cranach's painting of a classical nymph represents an Italian theme but gives it a moralizing twist common to late Gothic courtly and amorous subjects.
The nymph reclines beside a spring, perhaps a reference to a legendary ancient Roman fountain with which a Latin verse was associated. The text was translated by Alexander Pope in 1725:
Nymph of the grot, these springs I keep, And to the murmurs of these waters sleep; Ah, spare my slumbers, gently tread the cave! And drink in silence, or in silence lave!
The inscription on this painting -- I am the nymph of the sacred spring, do not disturb my sleep. I am resting -- may be an allusion to the poem. Though exposed by modern scholarship as a fifteenth-century counterfeit, the poem influenced Italian garden decoration, which not infrequently included fountains with attendant reclining nymphs. However, the proportions of Cranach's nude are more Gothic than classical, and the robe on which she rests her head is that of a German court lady. Far from sleeping, she admires herself beguilingly through lowered eyelids. The painting is intended both as an enticement and a warning to Cranach's sophisticated patrons.
More information on this painting can be found in the Gallery publication German Paintings of the Fifteenth through Seventeenth Centuries, which is available as a free PDF https://www.nga.gov/content/dam/ngaweb/research/publications/pdfs/german-painting-fifteenth-through-seventeenth-centuries.pdf
upper left: FONTIS NYMPHA SACRI SOM: / NVM NE RVMPE QVIESCO (I am the Nymph of the Sacred Spring. Do not disturb my sleep. I am resting.); to the right of the inscription, the artist's device, a serpent with folded wings holding a ring in its mouth, facing left
Probably Baron von Schenck, Flechtingen Castle, near Magdeburg. (Bohler and Steinmeyer, Lucerne and New York, 1931-1933). Clarence Y. Palitz [d.1958], New York, by 1939; gift (partial and promised)1957 to NGA; gift completed 1958.
- Classics of the Nude, M. Knoedler & Co., New York, 1939, no. 5A.
- Masterpieces of Art. European Paintings and Sculpture from 1300-1800, New York World's Fair, 1939, no. 59, repro.
- Golden Gate International Exposition, Palace of Fine Arts, San Francisco, 1940, no. 137.
- Felipe II: El Rey íntimo. Jardín y naturaleza en el siglo XVI, Palacio del Real Sitio de Aranjuez, Madrid, 1998, no. 253, repro.
- Kleopatra blir Ariadne. Identitet och Förvandling [From Cleopatra to Ariadne. Identity and Transformation], Prins Eugens Waldemarsudde, Stockholm, 2003-2004, no. 2, repro.
- Cranach et son temps, Palais des Beaux-Arts, Brussels; Musée du Luxembourg, Paris, 2010-2011, no. 112, repro.
- Lucas Cranach, the Elder: 500 Years of the Power of Temptation, The National Museum of Western Art, Tokyo; The National Museum of Art, Osaka, 2016-2017, no. 56, repro.
The panel is composed of three boards with horizontal grain, each of which varies in height from one side to the other. The panel has been thinned, probably at the time the cradle was attached, and the top and right edges may have been slightly trimmed. Examination with infrared reflectography did not disclose underdrawing, although it did indicate that the left branch of the tree on the right was painted later than the trunk. There are also pentimenti visible to the naked eye in the contour of the lower part of the nymph's leg and right forearm and in the townscape.
The painting is generally in good condition but has suffered some damage. There are checks at the left and right sides, chips missing from the top left and right corners, and a few small drill holes on the top and bottom edges. On the top left edge there are two large losses that have been filled and retouched, and there is scattered retouching throughout.
 The wood was identified as linden by Peter Klein, examination report, 29 September 1987, in NGA curatorial files, and by the National Gallery's scientific research department.
- Friedländer, Max J. and Jakob Rosenberg, Die Gemälde von Lucas Cranach. Berlin, 1932: 89, no. 324, repro. (Rev. ed. The Paintings of Lucas Cranach. Amsterdam, 1978: 150, no. 403, repro.
- Rosten, Leo. "Cranach--The Impish Nude." Look (20 January, 1959): repro. (Repr. in The Story Behind the Painting. New York, 1962: 52, color repro. 53).
- Summary Catalogue of European Paintings and Sculpture. National Gallery of Art, Washington, 1965: 34.
- Galvan, Jose Maria Moreno, ed. Galleria Nazionale di Washington. Madrid, 1968: 35, fig. 5, 26.
- Liebmann, Michael. "On the Iconography of the Nymph of the Fountain." Journal of the Warburg and Courtauld Institutes 31 (1968): 436.
- National Gallery of Art. European Paintings and Sculpture, Illustrations. Washington, 1968: 27, repro.
- Talbot, Charles W. Jr. "An Interpretation of Two Paintings by Cranach in the Artist's Late Style." Studies in the History of Art 1967 (1968): 68, 78-85, fig. 8.
- Bonicatti, Maurizio and Claudia Cieri. "Lucas Cranach alle soglie dell'Umanesimo italiano." The Journal of Medieval and Renaissance Studies 4 (1974): 280, n. 42.
- European Paintings: An Illustrated Summary Catalogue. National Gallery of Art, Washington, 1975: 86, repro.
- Walker, John. National Gallery of Art, Washington. New York, 1975: 165, no. 189, repro.
- Koepplin, Dieter and Tilman Falk. Lukas Cranach: Gemälde, Zeichnungen, Druckgraphik. Exh. cat. 2 vols. Kunstmuseum, Basel, 1976: 2:638, under no. 547.
- Börsch-Supan, Helmut. "Cranachs Quellnymphen und sein Gestaltungsprinzip der Variation." In Akten des Kolloquiums zur Basler Cranach-Ausstellung, 1974. Basel, 1977: 21.
- Wolff, Martha. German Art of the Later Middle Ages and Renaissance in the National Gallery of Art. Washington, 1983: unpaginated, repro.
- Walker, John. National Gallery of Art, Washington. Rev. ed. New York, 1984: 165, no. 183, color repro.
- European Paintings: An Illustrated Catalogue. National Gallery of Art, Washington, 1985: 105, repro.
- Gregory, Clive, ed. "Cranach." In The Great Artists: Their Lives, Works, and Inspiration 41. 4 vols. London 1985: 2:1304-1305, repro.
- Circa 1492: Art in the Age of Exploration. Exh. cat. National Gallery of Art, Washington, D.C., 1991: 259-260, no. 158, color repro. 260 (the painting was not in the exhibition).
- National Gallery of Art, Washington. National Gallery of Art, Washington, 1992: 71, repro.
- Hand, John Oliver, with the assistance of Sally E. Mansfield. German Paintings of the Fifteenth through Seventeenth Centuries (The Collections of the National Gallery of Art Systematic Catalogue). Washington, 1993: 34-40, color repro. 37.
- Löcher, Kurt. Review of German Paintings of the Fifteenth through Seventeenth Centuries, by John Oliver Hand with the assistance of Sally E. Mansfield. Kunstchronik 43 no. 1 (January 1995): 15.
- Apostolos-Cappadona, Diane. Encyclopedia of Women in Religious Art. New York, 1996: 87, fig. 27.
- Schoon, Peter and Sander Paarlberg, eds. Greek Gods and Heroes in the Age of Rubens and Rembrandt. Exh. cat. National Gallery/Alexandros Soutzos Museum, Athens; Netherlands Institute, Athens; Dordrechts Museum, Dordrecht, 2000-2001: 110, fig. 88 (the painting was not in the exhibition).
- Hand, John Oliver. National Gallery of Art: Master Paintings from the Collection. Washington and New York, 2004: 132-133, no. 100, color repro.
- Noll, Thomas. Albrecht Altdorfer in seiner Zeit: Religiöse und profane Themen in der Kunst um 1500. Munich, 2004: 396-397, 575 fig. 187.
- Depoorter, Matthias. "De onbekende wereld van Lucas Cranach." Review of De wereld van Lucas Cranach: Een kunstenaar in de tijd van Dürer, Titiaan en Metsys. Exh. Paleis voor Schone Kunsten, Brussels 2010. In Openbaar kunstbezit vlanderen 48, no. 5 (October-November 2010): 22-24, color repro.