who is its composer?
Mark Hall
If We Are the Body
If We Are the Body" is the debut single by Christian rock band Casting Crowns. Written by Mark Hall and produced by Mark A. Miller and Steven Curtis Chapman, it was released as the lead single from the band's 2003 self-titled debut album through Beach Street Records on July 26, 2003. 
story behind if we are the body by casting crowns The song was originally written for use as a "teaching tool" in Mark Hall's youth group.
wiki:10881451
If We Are the Body [SEP] Introduction
"If We Are the Body" is the debut single by Christian rock band Casting Crowns. Written by Mark Hall and produced by Mark A. Miller and Steven Curtis Chapman, it was released as the lead single from the band's 2003 self-titled debut album through Beach Street Records on July 26, 2003. The song, originally written by Hall as a "teaching tool" for his youth group, is a CCM and acoustic rock song. It incorporates the violin, mandolin, and accordion in its arrangement and questions why the Christian church does not minister impartially. "If We Are the Body" received positive reviews from music critics, who praised its lyrics and arrangement, and it was nominated for the awards for Song of the Year and Pop/Contemporary Recorded Song of the Year at the 35th GMA Dove Awards.