Final answer:
The sacrament that grants believers the strength of the Holy Spirit to defend and spread the Faith is Confirmation. It is a pledge to be an active and faithful member of the Church, building on the foundations of Baptism.
Step-by-step explanation:
The sacrament that grants believers a special strength of the Holy Spirit to defend and spread the Faith through both word and action is Confirmation. Confirmation is typically received in young adulthood and serves as the pledge to be a faithful member of the Church. It builds on the sacrament of Baptism, which is the rite of purification and initiation into Christianity, and is believed to be necessary to purge original sin. Confirmation endows the faithful with the Holy Spirit and empowers them to actively participate in the life and mission of the Church.