Source and decoding - Bava Batra 8b
גַּבָּאֵי תַמְחוּי שֶׁאֵין לָהֶם עֲנִיִּים לְחַלֵּק – מוֹכְרִין לַאֲחֵרִים וְאֵין מוֹכְרִין לְעַצְמָן. מָעוֹת שֶׁל צְדָקָה – אֵין מוֹנִין אוֹתָן שְׁתַּיִם, אֶלָּא אַחַת אַחַת.
Charity collectors with no poor to distribute to may exchange the coins with others but not with themselves.
Charity collectors with no poor to distribute to may exchange the coins with others but not with themselves. Charity coins are not counted two at a time but one by one. The rules aim to keep collectors above suspicion.