Top: optical arm of the spectra of the deflector (in rest frame), obtained from X-Shooter. The 4000 ﹩\dot{{\rm{A}}}﹩ break can be seen. The velocity dispersion can be inferred from the two characteristic absorption lines, e.g., [K] and [H] bands, of elliptical galaxies. Bottom: the spectra of the lensed source in the NUV, VIS, and NIR arms. The four arcs are decomposed from the two slits of different orientations (see Figure 1). The blue line shows the average flux of the four arcs. The Lyα, O II, and O III lines demonstrate that the background source is a Lyα emitter at z_s = 2.823.