This document provides biographical details about Daniel de la Sierra, a Claretian Missionary priest from Spain who served in Argentina. It describes his upbringing in rural Castile, his religious formation and studies in Rome, and his assignments teaching in Cordoba and pastoral work in the villas miseria (slums) of Buenos Aires. It outlines his commitment to serving the poor through religious, social, and political promotion work. The document also details his transfer in 1981 to neighborhoods in the south of Buenos Aires where he continued pastoral work, relying on his bicycle for transportation.