The den was sealed with a stone (Dan 6:17-6:18)

“A stone was brought.

They laid it

On the mouth

Of the den.

The king sealed it

With his own signet,

As well as with the signet

Of his lords.

Thus,

Nothing might be changed

Concerning Daniel.

Then the king

Went to his palace.

He spent the night

Fasting.

No food was brought

To him.

Sleep fled from him.”

They took a stone and put it at the mouth of the den. The king sealed the opening to the den with his own signet, as well as that of his lords. Nothing would be changed concerning Daniel. Then the king went to his palace that night and fasted. He did not sleep. He was still a little uneasy about this whole Daniel affair.