大方廣圓覺修多羅了義經略疏 2.171

2.171

障盡則行、住、坐、臥一切時中觸向無非解脫，故以清淨法殿喻之。

When obstacles are exhausted, then in walking, standing, sitting, and lying down, at all times, whatever is encountered is nothing but liberation; hence it is allegorized as the pure Dharma palace.