This phrase is used here to mark a stop in the main story. Here Luke starts to tell a new part of the story. (See: [[rc://en/ta/man/jit/writing-newevent]])
Here "eighth day" refers to the time after the birth of the baby, counted from the first day, which was the day he was born. Alternate translation: "on the eighth day of the baby's life" (See: [[rc://en/ta/man/jit/translate-ordinal]])
This was often a ceremony where one person circumcised the baby and friends were there to celebrate with the family. Alternate translation: "they came for the baby's circumcision ceremony" (See: [[rc://en/ta/man/jit/figs-explicit]])