Why would slaves be sacrificed after their master's death?

Question

Sacrifice is a common practice in the Norse pagan religion.

Sacrifice (blót) played a huge role in most of the rituals that are known about today, and communal feasting on the meat of sacrificed animals, [...] The purpose of these sacrifices was to ensure fertility and growth. However, sudden crises or transitions such as births, weddings and burials could also be the reason. In those times there was a clear distinction between private and public faith, and the rituals were thus tied either to the household and the individual or to the structures of society.

_{Source: Wikipedia}

The writings of Ibn Fadlan, specifically Ibn Fadlan and the Rusiyyah, inform us of a strange phenomenon of human sacrifice:

When their chieftain dies, his family ask his slave-girls and slave-boys, “Who among you will die with him?” and some of them reply, “I shall.” Having said this, it becomes incumbent upon the person and it is impossible ever to turn back. Should that person try to, he is not permitted to do so. It is usually slave-girls who make this offer. [...] I quizzed the interpreter about her actions and he said, “The first time they lifted her, she said, ‘Behold, I see my father and my mother.’ The second time she said, ‘Behold, I see all of my dead kindred, seated.’ The third time she said, ‘Behold, I see my master, seated in Paradise. Paradise is beautiful and verdant. He is accompanied by his men and his male- slaves. He summons me, so bring me to him.’” So they brought her to the ship and she removed two bracelets that she was wearing, handing them to the woman called the “Angel of Death,” the one who was to kill her.

_{Source: Ibn Fadlan and the Rusiyyah}

Why was there a need to sacrifice slaves after their master's death? Didn't people at the time believe that a chieftain, being a person of high importance, would enter Valhalla? If so, why would a slave be allowed to enter Valhalla?

Answer 1

Although slaves aren't specifically mentioned, Odin's burial laws tell us that "every one will come to Valhalla with the riches he had with him upon the pile":

Odin established the same law in his land that had been in force in Asaland. Thus he established by law that all dead men should be burned, and their belongings laid with them upon the pile, and the ashes be cast into the sea or buried in the earth. Thus, said he, every one will come to Valhalla with the riches he had with him upon the pile; and he would also enjoy whatever he himself had buried in the earth. For men of consequence a mound should be raised to their memory, and for all other warriors who had been distinguished for manhood a standing stone; which custom remained long after Odin's time. On winter day there should be blood-sacrifice for a good year, and in the middle of winter for a good crop; and the third sacrifice should be on summer day, for victory in battle. Over all Swithiod the people paid Odin a scatt or tax -- so much on each head; but he had to defend the country from enemy or disturbance, and pay the expense of the sacrifice feasts for a good year.

_{Source: THE YNGLINGA SAGA, OR THE STORY OF THE YNGLING FAMILY FROM ODIN TO HALFDAN THE BLACK.}

The logical conclusion, therefore, is that servants would be sacrificed in order to continue serving their master in the afterlife. How else could their master "enjoy whatever he himself had buried in the earth"?

Another hint that the sacrificed slaves were intended as a burial gift can be found in the poem The Short Lay of Sigurth:

68. "The door of the hall | shall strike not the heel
Of the hero fair | with flashing rings,
If hence my following | goes with him;
Not mean our faring | forth shall be.

69. "Bond-women five | shall follow him,
And eight of my thralls, | well-born are they,
Children with me, | and mine they were
As gifts that Buthli | his daughter gave.

_{Source: SIGURTHARKVITHA EN SKAMMA.}

Lastly, I think it's interesting to mention that Ibn Fadlan's narrative may be supported by archaeological finds:

Ten Viking Age individuals from the northern Norwegian site at Flakstad were analysed for δ13C, δ15N and ancient mitochondrial DNA fragments. The material derives from both single and multiple burials with individuals treated in different ways. The genetic analyses show that the individuals buried together were unlikely to be maternally related, and stable isotope analyses suggest different strata of society. It is, therefore, suggested that slaves may have been offered as grave gifts at Flakstad. A comparison with the remaining population from single graves shows that the presumed slaves had a diet similar to that of the common population, whereas the high status individuals in multiple graves had a diet different from both slaves and the common population. The results provide an insight into the subsistence of different social groups in a Viking Age society, exposing unexpected patterns of living conditions and food distribution.

_{Source: Slaves as burial gifts in Viking Age Norway? Evidence from stable isotope and ancient DNA analyses, Elise Naumanna, Maja Krzewińskab, Anders Götherströmd, Gunilla Erikssond.}