Pentecostals affirm the baptism in the Holy Spirit, an empowering encounter with the Spirit, often understood as distinct from and subsequent to conversion, that fills the believer for holy living and service. In classical Pentecostalism it is characteristically marked by speaking in tongues as the initial evidence, and it is associated with the reception of spiritual gifts for ministry and witness. The experience is modelled on the outpouring of the Spirit on the disciples at Pentecost (Acts 2) and on later episodes in Acts, which Pentecostals read as a pattern for the church in every age.
The experience is dated by Pentecostal historiography to Agnes Ozman speaking in tongues at Charles Parham's Bible school in Topeka, Kansas, on 1 January 1901, and to its wider public emergence at the Azusa Street Revival in Los Angeles (1906 to 1909), led by William J. Seymour, an African American preacher whose interracial meetings are widely credited with launching Pentecostalism as a movement. Pentecostals divide over how Spirit-baptism relates to conversion and sanctification: Wesleyan-Holiness Pentecostals hold it to be a third, distinct experience following a prior experience of entire sanctification, while Finished Work Pentecostals, following William Durham's teaching after 1910 and institutionalised in the Assemblies of God (founded 1914), hold sanctification to be gradual and Spirit-baptism a second, empowering experience following conversion directly.