The chemical composition of galaxies has been measured out to z \sim 4 . However , nearly all studies beyond z \sim 0.7 are based on strong-line emission from HII regions within star-forming galaxies . Measuring the chemical composition of distant quiescent galaxies is extremely challenging , as the required stellar absorption features are faint and shifted to near-infrared wavelengths . Here , we present ultra-deep rest-frame optical spectra of five massive quiescent galaxies at z \sim 1.4 , all of which show numerous stellar absorption lines . We derive the abundance ratios [ Mg/Fe ] and [ Fe/H ] for three out of five galaxies ; the remaining two galaxies have too young luminosity-weighted ages to yield robust measurements . Similar to lower-redshift findings , [ Mg/Fe ] appears positively correlated with stellar mass , while [ Fe/H ] is approximately constant with mass . These results may imply that the stellar mass-metallicity relation was already in place at z \sim 1.4 . While the [ Mg/Fe ] -mass relation at z \sim 1.4 is consistent with the z < 0.7 relation , [ Fe/H ] at z \sim 1.4 is \sim 0.2 dex lower than at z < 0.7 . With a [ Mg/Fe ] of 0.44 ^ { +0.08 } _ { -0.07 } the most massive galaxy may be more \alpha -enhanced than similar-mass galaxies at lower redshift , but the offset is less significant than the [ Mg/Fe ] of 0.6 previously found for a massive galaxy at z = 2.1 . Nonetheless , these results combined may suggest that [ Mg/Fe ] in the most massive galaxies decreases over time , possibly by accreting low-mass , less \alpha -enhanced galaxies . A larger galaxy sample is needed to confirm this scenario . Finally , the abundance ratios indicate short star-formation timescales of 0.2 - 1.0 Gyr .