What line from Act III of Hamlet supports the conclusion that Claudius fears his own fate?

And, like a man to double business bound,
I stand in pause where I shall first begin,
And both neglect.
What if this cursed hand
Were thicker than itself with brother’s blood,
Is there not rain enough in the sweet heavens
To wash it white as snow?
Bow, stubborn knees; and heart with strings of steel
Be soft as sinews of the new-born babe.
My words fly up, my thoughts remain below:
Words without thoughts never to heaven go.