(My bath awaits me!) Why the cauldron? Why

Not desecrate the dustbin? Here's the rub:

All the endorsements specify my tub;

The dustbin is not mentioned. Can I lie?

(My bath awaits me!) So I made a vow,

Soon as the groaning shelf could bear no more,

In one doomed bath to mix 'em. What I swore

I've done. The night of reckoning is now.

My bath awaits me! True. But then I said

Not "use" but "put." Why have my beastly bath?