Dear brother Asghar,
The verse alludes to the ancient method of kindling fire, rubbing two branches.
36:79 Say, “He Who brought them into being in the first place, will revive them again. He is the Profound Knower of all creation.
36:80 (The same Creator) Who produces for you fire out of the green tree when you kindle with it. [The flames are ‘hidden’ within the green branches! When the branch is ignited you can see this fire with your own eyes. Can He not preserve life in a similar manner?]