Quotation for Tahorot 8:9
מַקֵּל שֶׁהִיא מְלֵאָה מַשְׁקִין טְמֵאִין, כֵּיוָן שֶׁהִשִּׁיקָהּ לַמִּקְוֶה, טְהוֹרָה, דִּבְרֵי רַבִּי יְהוֹשֻׁעַ. וַחֲכָמִים אוֹמְרִים, עַד שֶׁיַּטְבִּיל אֶת כֻּלָּהּ. הַנִּצּוֹק וְהַקְּטַפְרֵס וּמַשְׁקֶה טוֹפֵחַ, אֵינָן חִבּוּר לֹא לַטֻּמְאָה וְלֹא לַטָּהֳרָה. וְהָאֶשְׁבֹּרֶן, חִבּוּר לַטֻּמְאָה וְלַטָּהֳרָה:
A stick which is full of impure liquid, once it touches a <i>mikvah</i> it becomes pure, according to Rabbi Yehoshua. And the Sages say: [it is not rendered pure] until one immerses its entirety. A shower [of liquids being poured], or [liquids flowing down] an incline, or a dripping liquid [enough to make something else wet, but not enough to, in turn, wet something else], these do not constitute a connection for impurity or for purity [i.e. if part of them is rendered pure or impure it does not affect the purity status of the rest]. But a pit [of stagnant water] does constitute a connection for impurity and for purity.