觀無量壽佛經義疏 3.85

3.85

「『舉足時，足下有千輻輪相，自然化成五百億光明臺。』」輪有千輻，號千輻輪。二、下足相。

"[The Buddha said:] 'When he raises his feet, beneath them is the mark of a thousand-spoked wheel, which naturally transforms into fifty billion light-platforms.'" The wheels having a thousand spokes are named "thousand-spoked wheels." Second, the aspect of lowering the feet.