When attending a Catholic Mass, it has become customary for the priest to elevate the Eucharistic host and the chalice after the words of consecration. This was not always the case, and took until the 13th century to become part of the Mass.
For much of Church history, the priest was accustomed to face the altar in the same direction as the people. This meant that when the priest was reciting the Eucharistic Prayer, the host and chalice were hidden from view.
Initially this did not pose any problem for the people, but by the 13th century, many saints were seeking ways to deepen the Eucharistic faith of the people.
For example, it was during the 13th century that St. Juliana of Liege pushed for the universal celebration of the Feast of Corpus Christi.
According to the New Catholic Encyclopedia, it was Odo of Paris or his successor in the early 13th century who, "decreed that his priests were to conceal the Host until it was consecrated and then to raise it up for adoration."
This decree was likely in response to requests from the laity, who wanted to see and adore Jesus in the Eucharist.
Even after the Second Vatican Council, when priests were permitted to celebrate Mass facing the people, the instruction remained in the Roman Missal for priests to "show the consecrated host to the people ... and genuflect in adoration."
The custom of showing the host and the chalice to the people has become a central part of the Mass, affirming the profound mystery that occurs at the consecration, where Jesus himself becomes present in the bread and wine that are offered on the altar.
