首楞嚴義疏注經 3.264

3.264

初二句合即唯身破，觸既合身，合應無二，唯一身根更無觸位。後二句離應無觸破，觸若離身，復何成觸，如虛空相亦無觸位。

The first two lines refute by showing that contact is only the body: since touch contacts the body, contact should leave no duality, being only the single body faculty with no further locus for touch. The latter two lines refute by showing that separation would leave no touch: if touch is separated from the body, how could it constitute touch again? Being like the mark of empty space, it also has no locus for touch.