I asked Abu Abdullah (as) about Qasamah (the collective oath) - where did it originate? Imam (as) said: "It began with the Messenger of Allah (swt) (peace be upon him and his family). After the conquest of Khaybar, a man from the Ansar was left behind by his companions. When they returned to search for him, they found him lying in his blood, killed. The Ansar came to the Messenger of Allah (swt) (peace be upon him and his family) and said: 'O' Messenger of Allah (swt), the Jews have killed our companion.' The Prophet (peace be upon him and his family) said: 'Fifty men from among you must swear an oath that they (Jews) killed him.' They said: 'O' Messenger of Allah (swt), how can we swear about something we did not witness?' Prophet (sw) said: 'Then the Jews will swear an oath.' They replied: 'O' Messenger of Allah (swt), who would believe the Jews?' The Prophet (peace be upon him and his family) said: 'Then I will pay the blood money for your companion.'" I asked Imam (as): "What is the ruling concerning Qasamah?" Imam (as) said: "Indeed, Allah (swt), the Almighty and Majestic, has ruled in matters of bloodshed in a way unlike any other matter of people's rights due to the sanctity of blood. If a man were to claim against another man ten thousand dirhams, whether less or more, the oath would not be upon the claimant but upon the one against whom the claim is made. However, when a man accuses a group of killing someone, the oath is upon the claimant of the blood before it is upon those accused. The claimant must bring fifty people to swear that a specific person killed another. Then, the accused is handed over to them. If they wish, they may forgive him, or if they wish, they may execute him, or if they wish, they may accept the blood money (diyyah). But if they refuse to swear, then fifty men from the accused group must swear, saying: 'We did not kill him, nor do we know his killer.' If they do so, the people of the village where the murder occurred must pay the blood money. If it happened in an isolated area, the blood money is paid from the public treasury (Bayt Al-Mal). The Commander of the Faithful (as) used to say: 'The blood of a Muslim must never be wasted.'"