מדרש על סנהדרין 5:2

5) (Vayikra 24:12) ("And they put him in confinement, to be explained to them at the mouth of the L–rd.") But they did not place the mekoshesh with him, though their situations were concurrent. And they knew that the mekoshesh was liable to the death penalty, viz. (Shemoth 21:14) "Those who desecrate it (the Sabbath) shall die, but they did not know which death penalty, viz. (Bamidbar 15:34) "for it was not clear what should be done to him," but here it is written "to be explained to them at the mouth of the L–rd" — whereby we are taught that they did not know whether he was liable to the death penalty or not.