The word: رجم (rajm) in: يَرْجُمُوكُمْ means they will stone you to death - 19.' It will be recalled that the king had warned them - before they went to the Cave - that they will be killed if they kept adhering to their present faith. This verse Al-Kahf 18:20 ⧉ tells us that a renegade in their faith used to be punished by being stoned to death in which everyone participated, expressed collective anger and lent a hand in killing him.
Perhaps, the punishment for adultery committed by a married man or woman by stoning to death, as proposed in the Shari` ah of Islam, may be aimed at exposing the one guilty of this abominable act at the cost of all norms of modesty and propriety. The execution of the culprit was to remain public with everyone joining in so that two things were ensured - let that disgrace be at collective level, and let all Muslims express their wrath practically so that no one dares repeat this act of shame among them.
The expression فَابْعَثُوا أَحَدَكُم (So send one of you — Al-Kahf 18:19 ⧉) tells us that the group in the Cave picked up a man from among them to go to the city and gave him the money to buy food which he would bring back. Al-Qurtubi finds this significant. He quotes Ibn Khuwaizmandad and describes some rulings deduced from here.
Rulings
1. Partnership in capital is permissible - because, this amount was shared by all.
2. Power of attorney or delegation of management is permissible in capital, that is, one person can, as an authorized agent disburse from shared capital with the permission of others.
If a group of people shares food, it is permissible - though, individual food intake usually differs with one eating less while the other, more.