Daniel 6:16-17

16So the king sent his servants to fetch Daniel. Then they threw Daniel into the cave where the lions lived. The king said to Daniel, ‘You have always continued to serve your God. I am sure that he will save you.’

17They took a big stone and they covered the top of the lions' cave. The king put a mark on the stone with his ring of authority. He also marked it with the rings of his important men. This meant that nobody could move the big stone to save Daniel.