'Harm' in the Bible

I saw another angel coming from the east having the seal of the living God. He cried out in a loud voice to the four angels who had been permitted to harm the land and sea,

"Don't harm the land, the sea, or the trees until we have marked the servants of our God with a seal on their foreheads."

They were told not to harm the grass on the earth, any green plant, or any tree. They could harm only the people who do not have the seal of God on their foreheads.