House of grass. Men like grass.

In book 9, chapter 7 Saints Gervase and Protase, page 216, it says "For long had I sighed after you, and at length I breathed in you, as far a breath my enter this house of grass."

The footnote after "house of grass" led me to Cf. Isa. 40:6, which says, " A voice says, 'Cry out.' And I said, 'What shall I cry?' All men are like grass, and all their glory is like the flowers of the field."

I am confused about the relationship between "men like grass" and a "house of grass."