Paschal Triduum in the context of Gemäldegalerie

Good Friday, also known as Holy Friday, Great Friday, Great and Holy Friday, or Friday of the Passion of the Lord, is a solemn Christian holy day commemorating the crucifixion of Jesus and his death at Calvary (Golgotha). It is observed during Holy Week as part of the Paschal Triduum.

Members of many Christian denominations, including the Catholic, Eastern Orthodox, Lutheran, Anglican, Methodist, Oriental Orthodox, United Protestant and some Reformed traditions (including certain Continental Reformed, Presbyterian and Congregationalist churches), observe Good Friday with fasting and church services. In many Catholic, Lutheran, Anglican and Methodist churches, the Service of the Great Three Hours' Agony is held from noon until 3 p.m.—the hours the Bible records darkness covering the land until Jesus' death on the cross. In the Catholic, Lutheran and Anglican traditions of Christianity, the Stations of the Cross are prayed in the evening of Good Friday, as with other Fridays of Lent. Communicants of the Moravian Church have a Good Friday tradition of cleaning gravestones in Moravian cemeteries.

Maundy Thursday, also referred to as Holy Thursday, or Thursday of the Lord's Supper, among other names, is a Christian feast during Holy Week that marks the beginning of the Paschal Triduum, and commemorates the Washing of the Feet (Maundy) and Last Supper of Jesus Christ with the Apostles, as described in the canonical gospels.

It is the fifth day of Holy Week, preceded by Holy Wednesday (Spy Wednesday) and followed by Good Friday. "Maundy" comes from the Latin word mandatum, or commandment, reflecting Jesus' words "I give you a new commandment." The date of the day will vary according to whether the Gregorian calendar or the Julian calendar is used. Eastern churches generally use the Julian system.

During the Liturgy of the Eucharist, the second part of the Mass, the elements of bread and wine are considered to have been changed into the veritable Body and Blood of Jesus Christ. The manner in which this occurs is referred to by the term transubstantiation, a theory of St. Thomas Aquinas, in the Roman Catholic Church. Members of the Orthodox, Anglican, and Lutheran communions also believe that Jesus Christ is really and truly present in the bread and wine, but they believe that the way in which this occurs must forever remain a sacred mystery. In many Christian churches, some portion of the consecrated elements is set aside and reserved after the reception of Communion and referred to as the reserved sacrament. The reserved sacrament is usually stored in a tabernacle, a locked cabinet made of precious materials and usually located on, above, or near the high altar. In Western Christianity usually only the Host, from Latin: hostia, meaning "victim" (the consecrated bread), is reserved, except where wine might be kept for the sick who cannot consume a host.

The reasons for the reservation of the sacrament vary by tradition, but until around 1000 AD the only reason for reserving the sacrament was to be taken to the ill, homebound, or dying (viaticum). After that devotional practices arose, as for Eucharistic adoration and for Communion services when a priest is unavailable to celebrate the Eucharist. During the Paschal Triduum, the sacrament is taken in procession from the tabernacle, if on the high altar or otherwise in the sanctuary, to the Altar of Repose, and reserved from the end of the Mass of the Lord's Supper until the Communion Rite on Good Friday (called the Mass of the Presanctified, since the Eucharistic Prayer and consecration are omitted in the Good Friday celebration); this period is seen by some as symbolic of the time between the Last Supper and the Crucifixion of Jesus. The Blessed Sacrament is then absent from the tabernacle until the end of the Easter Vigil.