The arabic lettering in the graphic is arranged to summarize the relationship between the two brothers to their father and his house. Kenneth E. Bailey explains the typography in The Cross and the Prodigal:
The decorative Arabic calligraphy says “And he said, ‘A certain man had two sons.’”The characters on the right symbolize the younger son, who stands outside his father’s fellowship in rebellion. The older son (the characters on the left) seems to have a tenuous hold within the house, but in reality he too stands outside.
Graphics like this serve as visual tools for Christian missionaries when they share stories cross-culturally.