[en] We report the discovery of RG1M0150, a massive, recently quenched galaxy at z = 2.636 that is multiply imaged by the cluster MACSJ0150.3-1005. We derive a stellar mass of $\mathrm{l}\mathrm{o}\mathrm{g}{M}_{\ast <!--\; ???\; -->}={11.49}_{-<!--\; ???\; -->0.16}^{+0.10}$ and a half-light radius of $R_{e,\mathrm{m}\mathrm{a}\mathrm{j}}=1.8\pm <!--\; ??\; -->0.4\mathrm{k}\mathrm{p}\mathrm{c}.$ Taking advantage of the lensing magnification, we are able to spatially resolve a remarkably massive yet compact quiescent galaxy at $z><!--\; >\; -->2$ in ground-based near-infrared spectroscopic observations using Magellan/FIRE and Keck/MOSFIRE. We find no gradient in the strength of the Balmer absorption lines over $0.6R_e-<!--\; ???\; -->1.6R_e,$ which are consistent with an age of 760 Myr. Gas emission in [N ii] broadly traces the spatial distribution of the stars and is coupled with weak Hα emission (log [N ii]/$\mathrm{H}\mathrm{\alpha <!--\; ??\; -->}=0.6\pm <!--\; ??\; -->0.2$), indicating that OB stars are not the primary ionizing source. The velocity dispersion within the effective radius is ${\mathrm{\sigma <!--\; ??\; -->}}_{e,\mathrm{s}\mathrm{t}\mathrm{a}\mathrm{r}\mathrm{s}}=271\pm <!--\; ??\; -->41$ km s${}^{-<!--\; ???\; -->1}.$ We detect rotation in the stellar absorption lines for the first time beyond $z\sim <!--\; ???\; -->1.$ Using a two-integral Jeans model that accounts for observational effects, we measure a dynamical mass of $\mathrm{l}\mathrm{o}\mathrm{g}{M}_{\mathrm{d}\mathrm{y}\mathrm{n}}=11.24\pm <!--\; ??\; -->0.14$ and $V/\mathrm{\sigma <!--\; ??\; -->}=0.70\pm <!--\; ??\; -->\mathrm{0.21.}$ This is a high degree of rotation considering the modest observed ellipticity of 0.12 ± 0.08, but it is consistent with predictions from dissipational merger simulations that produce compact remnants. The mass of RG1M0150 implies that it is likely to become a slowly rotating elliptical. If it is typical, this suggests that the progenitors of massive ellipticals retain significant net angular momentum after quenching which later declines, perhaps through accretion of satellites.