Two baptisms followed their fervent praying: the baptism of water, to symbolically wash away their sins—burying the old man of sin and rising to newness of life, in the likeness of the Resurrection—and the baptism of fire, to symbolically burn away their sins to provide a worthy vessel for the Spirit of the Lord to reside in. The two baptisms feature two great cleansing agents—water and fire—to purify and sanctify souls to become holy as God is holy.
The symbol of the Holy Ghost is fire. The people were encircled about “as if it were by fire”—again not our usual fire, but the radiance, brilliance, light, or glory that accompanied angelic ministrants from heaven (see commentary at Helaman 5:23–50, especially verse 45, and 3 Nephi 25:1).