首楞嚴義疏注經 5.206

5.206

室利羅，云如來體骨。然燈塗金皆是身金光耀之因，累劫皆爾，非止一佛，故得然也。經出別緣，各從一說。

Śarīra is translated as the Tathāgata's bodily bones. Lighting lamps and applying gold are both the causes for the body's golden radiance; over accumulated kalpas it was always thus, not limited to a single Buddha, hence it could be accomplished like this. Sūtras set forth distinct karmic causes, each following a particular exposition.