The primary event of Idul Adha is a great feast that all Muslims partake in. This meal originated from Ibrahim’s sacrifice of a sheep after Allah was pleased with Ibrahim’s obedience and chose to spare the life of Ishmael. On Idul Adha, every Muslim family that can afford to is expected to sacrifice a sheep, goat or cow.
The animal’s meat is divided into three portions. The first portion is for the family members of the person who owns the animal. The second portion is given to relatives, and the third portion is distributed to families who cannot afford to sacrifice an animal of their own.
On the morning of Idul Adha, Muslims perform their pre-sunrise prayers. Then, at a mosque, Muslims perform the Idul Adha prayer when the sun is at its highest point in the sky. Idul Adha is a formal Islamic holiday, so Indonesian Muslims will often wear traditional clothing to attend mosque services.
This description by Indonesian Public Holidays.