Reference for Makhshirin 1:5

הַמְמַחֵק אֶת הַכְּרֵישָׁה, וְהַסּוֹחֵט שְׂעָרוֹ בִּכְסוּתוֹ, רַבִּי יוֹסֵי אוֹמֵר, הַיּוֹצְאִין בְּכִי יֻתַּן, וְאֶת שֶׁבּוֹ אֵינָן בְּכִי יֻתַּן, מִפְּנֵי שֶׁהוּא מִתְכַּוֵּן שֶׁיֵּצְאוּ מִכֻּלּוֹ:

[If] one squeezes a leek or wrings [water] from his hair with his clothing, Rabbi Yose says: The [water] that emerges achieves <i>BeKhi Yutan</i> but what [remains] in it [that subsequently emerges] does not achieve <i>BeKhi Yutan</i> because he intends that all [the water] should emerge from it.

Jastrow