Reference for Tahorot 9:2
גָּמַר מִלִּמְסֹק אֲבָל עָתִיד לִקַּח, גָּמַר מִלִּקַּח אֲבָל עָתִיד לִלְווֹת, אֵרְעוֹ אֵבֶל, אוֹ מִשְׁתֶּה, אוֹ אֹנֶס, אֲפִלּוּ זָבִים וְזָבוֹת מְהַלְּכִים עֲלֵיהֶן, טְהוֹרִין. נָפְלוּ עֲלֵיהֶן מַשְׁקִין טְמֵאִין, אֵין טָמֵא אֶלָּא מְקוֹם מַגָּעָן, וְהַמֹּחַל הַיּוֹצֵא מֵהֶן טָהוֹר:
If one finished harvesting [his olives] but intends to buy, or finished buying but intends to borrow [more olives], if it happened that he became a mourner, or had a feast [to attend], or something unavoidable befell him [preventing him from getting more olives or pressing them], even if <i>zavim</i> and <i>zavot</i> [certain individuals with discharges that render them a Source of impurity] walk upon them [i.e. upon the olives he already had] they remain pure [as they have not become primed for impurity]. If impure liquids fell on them, only the area they touched is impure, and the sap that emerges from them is pure.