The pentagram is known to the Baha'i as the haykal, which is an Arabic word meaning "temple" or "body." While the nine-pointed star is the symbol most commonly associated with the Baha'i today, it is the haykal that Shoghi Effendi declared as the official symbol.
In particular, the haykal represents the body of the Manifestations of God, of which Baha'u'llah is the most recent.
The Bab, under whom Baha'u'llah studied, used the haykal as a graphical template for numerous writings, such as the one depicted here. The lines are composed of Arabic writing arranged in the shape of a pentagram.