אַ֣ךְ מַעְיָ֥ן וּב֛וֹר מִקְוֵה־מַ֖יִם יִהְיֶ֣ה טָה֑וֹר וְנֹגֵ֥עַ בְּנִבְלָתָ֖ם יִטְמָֽא׃
Nevertheless a fountain or a cistern wherein is a gathering of water shall be clean; but he who toucheth their carcass shall be unclean.
Read kabbalistic (mystical) interpretation of Leviticus 11:36: and classical mystical sources.