  We report the discovery and spectroscopic confirmation of three
gravitationally-lensed images of a galaxy at z=3.9 in the background of a
distant, rich cluster of galaxies at z=0.83, on the basis of observations with
Faint Object Camera And Spectrograph (FOCAS) on the Subaru telescope. We
construct a simple lens model of the cluster mass distribution based on Jee et
al.'s weak lensing mass estimates from deep, high-resolution images by Advanced
Camera for Surveys (ACS) on the Hubble Space Telescope. The lens model can
account simultaneously for the observed image configuration and the flux ratio
of the closer pair located close to the critical curve. The parities of the
three images are also consistent with the lensing hypothesis. Since this galaxy
is apparently bright (i'_{AB} \sim 23.7) for its redshift due to the
magnification, it serves as a good high redshift target on which we can make
extensive and detailed studies based on multi-wavelength imaging and
spectroscopy.
