Eid ul-Adha also known as the Feast of the Sacrifice is the second and the biggest celebration within Islam. This Eid honours the willingness of the Islamic Prophet Ibrahim, also known as Abraham, to sacrifice his son Ismail as an act of obedience to Allah's command.
The celebration of Eid-ul-Adha is to commemorate Prophet Ibrahim's devotion to Allah SWT and his readiness to sacrifice his son, Ismail. At the very point of sacrifice, Allah SWT replaced Ismail with a ram, which was to be slaughtered in place of his son.