What are the Catholic Church's instruction on kneeling down in prayer in churches?

What are the Catholic Church's instruction on kneeling down in prayer in churches?

Kneeling at Mass has been traditionally been done for centuries at Catholic Masses. Both the Ordinary Form of the Mass and the Extraordinary Form of the Mass have rules governing bodily positions while being present at Mass.

Movements and Posture

42. The gestures and posture of the priest, the deacon, and the ministers, as well as those of the people, ought to contribute to making the entire celebration resplendent with beauty and noble simplicity, so that the true and full meaning of the different parts of the celebration is evident and that the participation of all is fostered. Therefore, attention should be paid to what is determined by this General Instruction and the traditional practice of the Roman Rite and to what serves the common spiritual good of the People of God, rather than private inclination or arbitrary choice.

A common posture, to be observed by all participants, is a sign of the unity of the members of the Christian community gathered for the sacred Liturgy: it both expresses and fosters the intention and spiritual attitude of the participants.

43. The faithful should stand from the beginning of the Entrance chant, or while the priest approaches the altar, until the end of the collect; for the Alleluia chant before the Gospel; while the Gospel itself is proclaimed; during the Profession of Faith and the Prayer of the Faithful; from the invitation, Orate, fratres (Pray, brethren), before the prayer over the offerings until the end of Mass, except at the places indicated below.

They should, however, sit while the readings before the Gospel and the responsorial Psalm are proclaimed and for the homily and while the Preparation of the Gifts at the Offertory is taking place; and, as circumstances allow, they may sit or kneel while the period of sacred silence after Communion is observed.

In the dioceses of the United States of America, they should kneel beginning after the singing or recitation of the Sanctus until after the Amen of the Eucharistic Prayer, except when prevented on occasion by reasons of health, lack of space, the large number of people present, or some other good reason. Those who do not kneel ought to make a profound bow when the priest genuflects after the consecration. The faithful kneel after the Agnus Dei unless the diocesan Bishop determines otherwise

With a view to a uniformity in gestures and postures during one and the same celebration, the faithful should follow the directions which the deacon, lay minister, or priest gives according to whatever is indicated in the Missal.

General Instruction of the Roman Missal (Institution Generalis Missalis Romani) Including Adaptations for the Dioceses of the United States of America March 17, 2003

Although some local customs and traditions may see less kneeling at Mass in some regions, the posture of kneeling is a tradition not only of the Tridentine Mass, but of tradition dating back to antiquity.

The physical posture is an ancient one, used by Christians since the very beginning.

For Roman Catholics, kneeling is one of the most distinctive physical gestures of prayer during the celebration of Mass. In fact, for many centuries the lay faithful of the Roman Rite would kneel for almost the entire duration of Mass.

Why is that?

While it’s true that standing during prayer was a common posture of the early Christians (and is currently maintained by many Eastern Christians during the Divine Liturgy), kneeling was also part of early Christian tradition.

According to Cardinal Joseph Ratzinger (Pope Benedict XVI), kneeling was something highly disfavored by both Greek and Roman culture. Ratzinger writes in his book Spirit of the Liturgy, “If we look at history, we can see that the Greeks and Romans rejected kneeling … kneeling was unworthy of a free man, unsuitable for the culture of Greece, something the barbarians went in for. Plutarch and Theophrastus regarded kneeling as an expression of superstition … Aristotle called it a barbaric form of behavior.”

Ratzinger claimed that, “Kneeling does not come from any culture — it comes from the Bible and its knowledge of God.” In particular, “Saint Luke, who in his whole work (both the Gospel and the Acts of the Apostles) is in a special way the theologian of kneeling prayer, tells us that Jesus prayed on His knees. This prayer, the prayer by which Jesus enters into His Passion, is an example for us.”

Catholics kneel because Jesus kneeled during prayer.

Additionally, kneeling is typically seen in the Gospels as a way to express supplication and adoration. Often in the New Testament kneeling is preceded by an act of faith, “I do believe, Lord,” and completed by an act of adoration at the majesty of God (cf. John 9:35-38).

Elsewhere, like in many of the healing narratives, the person is presented kneeling in supplication, asking to be healed.

For these reasons the Roman Rite instructs the faithful to kneel during Mass specifically when Jesus is made present on the altar. According to the General Instruction of the Roman Missal, “In the Dioceses of the United States of America, [the faithful] should kneel beginning after the singing or recitation of the Sanctus (Holy, Holy, Holy) until after the Amen of the Eucharistic Prayer.”

This physical posture is meant to express a spiritual attitude of adoration before the triune God, truly and substantially present in the Holy Eucharist. It is an act of humility, recognizing our own littleness before the Creator of the world. The act of kneeling prepares our hearts to receive God within our souls, striking down our pride with a physical reminder of what our soul should be like spiritually. - Why do Roman Catholics kneel at Mass?

There is a tradition that St. James the Apostle spent so much time kneeling in prayer that he had knees as hard as a camel's.

St. Emiliana was said to have skin as hard as the hide of a camel at her death. She prayed for countless hours on her knees each day.

The skin of her knees and elbows was found to be hardened, "like the hide of a camel", by her continual prayer. - St. Emiliana