Garuḍa Purāṇa 6

It is said that the distance between the earth and the world of Yama is 86,000 yojans. One yojana approximately measures nine miles. The servants of Yama dragging the subtle body of the dead cover this distance in 48 days. The path of this journey is not the same for everyone.  Yama’s servants inflict tremendous amount of torture on the subtle body of the sinners.  The intensity of the torture depends upon the sins committed by the dead when he was alive. In the world of Yama, there are sixteen cities. The subtle body of the dead passes either through all these cities or select cities depending upon his sins and survives only on the piṇḍa-s offered by his sons. His subtle body covers all the cities in twelve months. It is said that in order to satiate the hunger of the dead, piṇḍa-s are offered every month for one year.  But whatever is offered to the dead in the first 48 days is consumed by the dead and reduces the suffering during its travel from the earth to Yama’s place.  The hunger and thirst of the dead will be at their peak during eleventh and twelfth months which can be satiated only upon the food offered to Vedic scholars during these two monthly śraddha-s.  It is also said that monthly ceremonies during the first year are important, as the dead derive their energy only on the offerings made by his relatives.  

At the end of one year his sons perform first year śraddha rituals and the dead is allowed to eat piṇḍa offered during the ritual.  At the end of the first year, the subtle body after undergoing untold miseries in the hands of Yama’s servants attains a body depending upon his karmas.  This body is nothing but the sum total of his karmas.  This karmic body is taken to the place where Yama is seated.  There are fourteen gates to the place of Yama and each gate is guarded by a door keeper.  The gate keepers allow the karmic body of the dead inside Yama’s place depending upon rites performed by his relatives. These gate keepers are able to weigh the karmas done by the dead.  Depending upon his karmas, his karmic body is allowed to enter through a particular door to meet Yama directly.  Yama directs his servants to take the karmic body to be sent to good or bad states, depending upon one’s karmas, performed during his life time.

Yama changes his face on seeing every karmic body. On seeing the sinners, he becomes terrifying and on seeing the good ones, he becomes composed.  A person cannot make a living without committing a sin, either knowingly or unknowingly.  The only ritual that can keep Yama happy is the ritual of vṛṣotsarga.  It is a ritual when a bull is let loose on the eleventh day from the day of death.  Along with the bull a she calf should also be released. The details of the rituals are available in dharma śāstra-s. It is believed that the entire sins of the dead will be nullified if vṛṣotsarga ritual is performed.