The church has always taught that the body and blood of Christ are truly received in and under the bread and wine of the Lord’s Supper. The bread and the wine do not loose their natural substance but remain bread and wine. In the Sacrament Christ gives us His true body and true blood not just in a spiritual sense, as if the bread and wine are only a sign or figure of Christ’s body that has ascended to heaven. But as Christ says, His body and blood are received orally in the eating and the drinking. Even unworthy persons, hypocrites, or unbelievers receive Christ’s body and blood, not just those who believe His words. For this reason, those who despise or reject Christ’s words receive the Sacrament to their hurt and damnation. In this sacramental meal believers receive the forgiveness of sins, life and salvation, as the words “given and shed for you for the remission of sins” promise. Whoever believes it has what these words declare and bring: His merits, righteousness, and forgiveness. Instructive is Small Catechism VI 5–8, and Large Catechism V 28–32, 33–36, 69–72.
Find out more in Lutheranism 101: The Lord’s Supper