Priest of Urabrask

• WWizards of the Coast2011-01-25
  Official Ruling
  The triggered ability isn't a mana ability. It uses the stack and can be responded to.
• WWizards of the Coast2011-01-25
  Official Ruling
  You get the mana whether you want it or not. If you don't spend it, it will disappear at the end of the current step (or phase).

Rulings via Scryfall