Isaiah 11:6-8. The wolf also shall dwell with the lamb, and the leopard shall lie down with the kid; and the calf and the young lion and the fatling together; and a little child shall lead them. And the cow and the bear shall feed; their young ones shall lie down together, and the lion shall eat straw like the ox. And the suckling child shall play on the hole of the asp, and the weaned child shall put his hand on the cockatrice’ den. They shall not hurt nor destroy in all My holy mountain: for the earth shall be full of the knowledge of the Lord, as the waters cover the sea.”
It is important to remember that these prophecies are not of heaven, but of the Millenial Kingdom in which Jesus rules for 1000 years from His throne in Jerusalem. Also, these verses (6-8) are not symbolic; that is, they are to be interpreted literally.
It is the presence of Jesus Christ, Messiah, that characterizes the safety of this period of time, when animals who have been natural enemies since the Fall are no longer hunting each other for food. Even the lion will eat straw, like the ox. A baby can play safely on the nest of the asp, and a toddler can touch the hole of the adder’s den. There will be no fear as the personality and holiness of Jesus influence the earth and all that the earth contains.
The holy mountain is the land of Zion, the governmental center of the whole earth. The phrase as the waters cover the sea pictures the depth and fullness of the knowledge of Jehovah. The whole earth will be blessed by His presence.