Tractate Makhshirin - Chapter 1 - Mishnah 2 מכשירין פרק א׳ משנה ב׳

If one shook a tree in order to cause food or something unclean to fall down from it, [the rain water dropping down from it] does not come under the law of ‘if water be put.' If [he shook the tree] in order to cause liquids to fall down from it: Bet Shammai says: both [the liquids] that fall down and [the liquids] that remain [on the tree] come under the law of ‘if water be put.' But Bet Hillel say: [the liquids] that fall down come under the law of ‘if water be put’, but [the liquids] that remain [on the tree] do not come under the law of ‘if water be put,' because his intention was that [the liquids] should drop down from all the tree.