The ritual slaughter, known as Qurbān, Nusuk, Naḥr or Uḍḥiya, is a ritual performed towards the end of the pilgrimage (Ḥaǧǧ). It is a confirmed Sunnah (Sunnah Muʾakkadah) and according to some scholars also an obligation for those who have the financial means.
The foundation of this sacrifice is the willingness of the prophet Ibrāhīm (peace be upon him) to sacrifice his son Ismāʿīl to Allāh, when he received such order. As it is told in the following verse:
And when he reached with him [the age of] exertion, he said,
“O my son, indeed I have seen in a dream that I [must] sacrifice you, so see what you think.” He said,
“O my father, do as you are commanded. You will find me, if Allah wills, of the steadfast.”
(Sūrah aṣ-Ṣāffāt, Vers 102)
And when they had both submitted and he put him down upon his forehead, We called to him,
„O Abraham, You have fulfilled the vision.” Indeed, We thus reward the doers of good. Indeed, this was the clear trial. And We ransomed him with a great sacrifice.“
(Sūrah aṣ-Ṣāffāt, Verse 103-107)
This act symbolizes the surrender and thus the act of sacrifice of an animal towards the end of the pilgrimage is an expression of gratitude and devotion for the mercy and gifts of Allāh.
The specific amount, which should be slaughtered per household/family, is one to two sheep or 1/7 of a cow or a camel. The animals should be strong and healthy.