Answer:
It holds most knowledge that has ever been said. But is not the brain, is not the head. To feathers and their masters, it's both bane and boonΒ One empty, and one full.
My life can be measured in hours. I serve by being devoured. Thin, I am quick. Fat, I am slow. Wind is my foe.
Sleeping during the day, I hide away. Watchful through the night, I open at dawn's light. But only for the briefest time, do I shine. And then I hide away. And sleep through the day.
Kills the bad ones and the sad ones. Tightens to fit, so one size fits.
What does man love more than life, fear more than death or mortal strife. What the poor have, the rich require, and what contented men desire. What the miser spends, and the spendthrift saves. And all men carry to their graves.
What is always coming but never arrives?