107. This is to emphasize that there is no power that can deliver them from that everlasting torment. Of course, Allah has full powers to forgive anyone He wills or to make a change in the term of the torment of anyone, for He Himself devises laws for Himself and there is no law higher than His Law so as to limit His powers.
108. In (Ayats 107-108), the words “the heavens and the earth” might have been used idiomatically to denote the everlasting state or they might refer to the new earth and the heavens that will be made in the next world. Anyhow these cannot be the earth and the heavens in their existing state for two reasons. First, according to the Quran, they shall be changed on the Day of Resurrection. Secondly, the events that are being related in these verses will happen in the Hereafter.
109. That is, they will not be sent to the Garden nor will dwell there in accordance with any extraneous law which might have forced Allah to let them dwell therein anyhow. They shall dwell there simply because of His favor. He has full powers to make any changes, if He will, about them.