I begin a selfless task with no thought of reward. While working, the possibility of being rewarded for my task occurs to me.
Does this new thought invalidate the selflessness of my action, even though I began with "pure" motives? If I am able to drive thoughts of reward from my mind until I am done, does my action become selfless again?
If the thought of reward spurs me on to do an even better job, does that tilt the scales even further away from my selflessness, or does it remain steady, because the task was only begun with "pure" intentions?