Likely the bull was slaughtered as a fellowship or peace offering to the Lord (cf. Leviticus 3:1–17; Numbers 15:8–9). This sacrifice was one in which the people received a large portion of the animal back in order to eat it. The idea was that the worshipper and his family were eating holy food in the presence of the Lord. It conveyed the idea of thanksgiving and a feast being provided by God.
25 Then they slaughtered the bull, and they brought the child to Eli.