What is the source of the allusion in the sentence below?
A modern-day Icarus, Maddie launched into the first stretch of the marathon at a breakneck pace.

 - Greek mythology
 - Shakespeare
The source of the allusion Icarus is Greek mythology.
In Greek mythology, Icarus's father Daedalus built wings for his son but warned him not to fly too high. Too excited to heed his father's advice, Icarus flew so close to the sun that his wings melted and he fell from the sky.
The allusion Icarus means an overconfident person who ignores his or her limitations.