They were told not to harm the grass of the earth or any plant or tree, but only those who did not have the seal of God on their foreheads.
KJV
And it was commanded them that they should not hurt the grass of the earth, neither any green thing, neither any tree; but only those men which have not the seal of God in their foreheads.
ASV
And it was said unto them that they should not hurt the grass of the earth, neither any green thing, neither any tree, but only such men as have not the seal of God on their foreheads.