'Grass' in the Bible

The first sounded, and there followed hail and fire, mixed with blood, and they were thrown to the earth. One third of the earth was burnt up, and one third of the trees were burnt up, and all green grass was burnt up.

They were told that they should not hurt the grass of the earth, neither any green thing, neither any tree, but only those people who don't have God's seal on their foreheads.