Tosefta zu Bamidbar 32:22

Charity collectors may not spread out from each other [each one collecting in a different place, see Bava Batra 8b:16, Steinsaltz tr.]. [Moreover,] even if his friend gave him money that he owed him, even if he found money on the road, he does not have the right to take it with him [as others may mistakenly believe that he is enriching himself with communal funds], as it is said (Num. 32:22, Fox tr.), "and you will be clear [of obligation] before YHWH and before Israel." However, [charity collectors] may spread out from each other inside a courtyard or inside a store and collect [separately].