 He worked in the Congregation for the Doctrine of the Faith with the future Benedict XVI until 8 March 1996, when he was appointed Auxiliary Bishop of Bogotá and Titular Bishop of "Troyna" by Pope John Paul II.He received his episcopal consecration on the following 13 April from then-Archbishop Pedro Rubiano Sáenz, with Archbishops Paolo Romeo and Tarcisio Bertone, SDB, serving as co-consecrators.Ruiz Arenas was later named Bishop of Villavicencio on 16 July 2002, and was promoted to the rank of Archbishop when his see was elevated to an archdiocese on 3 July 2004.