瑜伽論記 6.287

6.287

二、解右脇而臥，而非如其餘鬼臥、天臥等者，謂若鬼覆面臥，若天仰面臥。其受欲者，左脇而臥，師子右脇而臥也。

Second, explaining lying on the right side and 'not like the sleeping of other ghosts, the sleeping of devas', and so forth: ghosts sleep lying face down, and devas sleep lying face up. Those who indulge in sensual desire sleep on their left side, while lions sleep on their right side.