Never trust a malicious Man upon the Account that thou hast done him good Offices: For thou hast but fed a Dragon that will devour thee, if ever thou comest within his reach.

Thomas Fuller (1654-1734) English physician, preacher, aphorist, writer

Introductio ad Prudentiam, Vol. 1, # 948 (1725)
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Fuller repeated this item as # 2443 in his second volume (1727), slightly altered:

Never trust a malicious Man upon the Account that thou hast done him good Offices. For thou hast but fed a Dragon, that will devour thee if ever thou comest within the Reach of his Claws.