identify the figure of speech for "how time on a Knife-edge can pass"?

I have never herd of this before but I would think that it would mean that the time would pass by painfully slow or would just be painful. Example 1: I spent 6 hours in the hospital waiting to find out if my friend was alright, it was painful waiting to find out. Example 2: I spent 6 hours in the hospital waiting to find out if my friend was alright, Oh "how time on a Knife-edge can pass". I hope this helps.

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