Parah 7:9

If one was carrying water for sanctification on his shoulder and he ruled in a matter of law, gave others directions, killed a snake or a scorpion, or picked up food in order to store it, the water is invalid; if he picked up food to eat, it is valid. If he killed a snake or a scorpion that was impeding him, the water is valid. Rabbi Yehuda said that the general rule is that if an act is a form of work, then the water is invalid whether the person carrying it stopped or not. If an act is not a form of work, then if he stops, the water is invalid but if he doesn’t stop, it’s valid.

Parah 7:10

If one handed his water to someone who was ritually unclean, it is invalid; to someone ritually clean, it is valid. Rabbi Eliezer says it even remains valid if handed to an unclean person so long as the owner didn’t perform some unrelated task.