Al-Jawharī said:
“Nusk means worship, and a nāsik is a worshipper. Nasaka and tanassaka mean ‘to worship’; nasuka, with the vowel u, means ‘to become a worshipper.’”
Pilgrimage was then singled out by the designation nusk because it involves worship and humility before Allah more fully than other acts. Hence it includes actions whose sole purpose is humility before Allah and worship of Him, such as the ritual passage between Safā and Marwah and the stoning of the pillars. The Prophet, may Allah bless him and grant him peace, said:
“The stoning of the pillars and the ritual passage between Safā and Marwah were instituted only to establish the remembrance of Allah.”
This was narrated by al-Tirmidhī. Slaughter offered as a sacrificial ransom is likewise singled out by this designation, unlike slaughter in general, because shedding blood for Allah expresses greater submission and worship of Him. For this reason, those before us did not eat their sacrificial offerings; rather, a fire would descend from heaven and consume them. Thus Allah Most High said:
“Those who said, ‘Allah has commanded us not to believe in any messenger until he brings us an offering consumed by fire.’ Say, ‘Messengers before me came to you with clear proofs and with what you speak of. Why, then, did you kill them, if you are truthful?’”
Likewise, whenever they acquired spoils of war, they would gather them together, and fire would come and consume them. This was so that their fighting would be purely for Allah, not for spoils, and their slaughter would be purely an act of worship for Allah, not for their own consumption. Allah granted greater latitude to the community of Muhammad, may Allah bless him and grant him peace, because of their perfect certainty and sincerity, and because they fight for Allah even if they partake of the spoils, and slaughter for Allah even if they eat of the offering.
For this reason, worshippers of devils and idols would likewise slaughter animals for them. Slaughtering for the object of one’s worship is the utmost expression of humility and submission to it. Hence it is not permissible to slaughter for anyone other than Allah, nor to invoke any name other than Allah’s over the animals being slaughtered.