Originally posted by Comprules:

116.4. If all players pass in succession (that is, if all players pass without taking any actions in between passing), the spell or ability on top of the stack resolves or, if the stack is empty, the phase or step ends.

Another judge asked me this question the other day, and while I believe I know the answer, I was unable to explain the reason why:

Player A casts a spell and passes priority. In response, Player B activates a mana ability but does not do anything with the mana. Does Player A's spell resolve, or does another priority pass occur?

I believe there is no second priority pass, but I was unable to explain to the other judge why. According to rule 116.4 (quoted above for your convenience), a second priority pass should occur, because activating a mana ability is an action, and any action should cause a second priority pass. However, I recall hearing that this is not the case. Am I mistaken, or is there something other than 116.4 that I'm not considering?

Edited Lyle Waldman (March 27, 2016 08:58:24 PM)

You are mistaken, I'm afraid.

As 116.4 says, all players pass(ing) in succession means all players passing without taking any actions in between passing. Activating a mana ability is taking an action, even if that mana isn't spent on anything. In the scenario you outlined, after Player B activates their mana ability and passes priority, the spell will not begin resolving because both players haven't passed in succession; instead, Player A will receive priority again.