Be careful then, patients,
and don’t accept any doctor;
die for free and do not give
a single coin to medicine.

Y así, enfermos, ojo alerta
y ningún médico admitan;
mueran de gorra sin dar
un real a la medicina.

Original text (Spanish)

Notes from Wikiquote

Quoted in Chambers Dictionary of Quotations (1997), p. 1038.