Unlike the joyful pilgrimage festivals, the Day of Atonement was marked by solemnity. Israel was called to humble itself before God while the high priest performed special rites of atonement.
In the Second Temple period the day focused attention upon the Jerusalem Temple even for people who were not physically present there.
Leviticus 16 describes the elaborate atonement rites involving the high priest, sacrifices, purification of the sanctuary, and the sending away of the scapegoat. Leviticus 23 establishes the day as a sacred occasion.
For ordinary people, the most noticeable feature was fasting and abstention from ordinary work. The day therefore changed the normal routines of eating, labor, and household activity.
The surviving remains of Jerusalem and the Temple Mount environment provide the physical setting of Second Temple worship, although the specific ritual installations described in ancient texts are not all archaeologically accessible.
Leviticus provides the biblical foundation. Josephus, Philo, later Jewish writings, and the New Testament book of Hebrews provide additional evidence for the importance and interpretation of the Day of Atonement.
Leviticus 16 presents the day as an annual purification and atonement for Israel and the sanctuary.
The Gospels do not narrate Jesus attending the Day of Atonement ceremonies. The New Testament book of Hebrews, however, uses the high priest and Day of Atonement imagery to explain the significance of Christ's sacrificial work.
The Day of Atonement was a major fast and sacred day centered upon atonement, purification, and the work of the high priest.
Household experience beyond fasting and cessation from work is less clearly documented than the Temple ritual itself.
The day provides essential background for biblical ideas of sin, sacrifice, priesthood, cleansing, and atonement.