大般涅槃經疏 31.13

31.13

「若有說言指住」下，第八重破空是住處，亦先牒、次破。所言指住處者，若言即指一切住處為虛空住處，既有四方，方若異者，空應四方隨空住處。

From "If someone says that pointing to an abode" downwards, the eighth [section] refutes again that space is an abode; it also first cites and next refutes. What is referred to as 'pointing to an abode' means: if one says that one directly points to all abodes as the abode of space, since there are four directions, if the directions are different, space should correspond to the four directions following the abode of space.