If memory serves, didn’t Lee encourage Jefferson Davis to free the slaves and was rejected?
Why would Lee encourage that? It's a serious question.
Confederate Gen. Patrick Cleburne supporting arming slaves in December of 1863, which would have required promising to free them as well. Basically what the Royal Governor of Virginia had done during the Revolution, Dunmore’s Proclamation.
Bruce Levine writes in his ‘Confederate Emancipation: Southern Plans to Free and Arm Slaves during the Civil War’ that Lee, Davis and Judah Benjamin came to the same conclusion in 1864 but it wasn’t tried until just a few weeks before Appomattox.