The answer is:
The pilgrims drew lots and he drew the shortest straw.
In "The Canterbury Tales," by Geoffrey Chaucer, Harry Bailey, the host and guide of the pilgrimage and owner of the Tabard Inn at Southwark, comes up with the idea of telling tales to pass the time on the journey. For that reason, the pilgrims draw lots to determine that the knight will tell the first tale. Nevertheless, the narrator does not think this is by chance. Actually, the knight is the first character to be portrayed because of his high social rank.
