What is the origin and basis of the idea of spending an hour each day in prayer?

Why should a Christian pray for one hour?

Traditional Catholics have a long tradition of praying for an hour before the Lord in the Blessed Sacrament. We call this devotion an Holy Hour!

Holy Hour is the Roman Catholic devotional tradition of spending an hour in Eucharistic adoration in the presence of the Blessed Sacrament. A plenary indulgence is granted for this practice. The practice is also observed in some Anglican churches.

In 1673 Saint Margaret Mary Alacoque stated that she had a vision of Jesus in which she was instructed to spend an hour every Thursday night to meditate on the sufferings of Jesus in the Garden of Gethsemane. This practice later became widespread among Roman Catholics.

The inspiration for the Holy Hour is Matthew 26:40. In the Gospel of Matthew, during the agony in the Garden of Gethsemane the night before his crucifixion, Jesus spoke to his disciples, saying "My soul is sorrowful even to death. Remain here and keep watch with me." (Matthew 26:38) Returning to the disciples after prayer, he found them asleep and in Matthew 26:40 he asked Peter:

"So, could you men not keep watch with me for an hour?".

In 1829, the Archconfraternity of the Holy Hour was established by Père Robert Debrosse at Paray-le-Monial, Burgundy, France. In 1911 it received the right of aggregation for the entire world. A similar society called "The Holy Perpetual Hour of Gethsemani" was formed in Toulouse in 1885 and was canonically erected in 1907. In 1909 it received indulgences from Pope Pius X.

The practice of a "daily Holy Hour" has been encouraged in the Catholic tradition, for instance Mother Teresa of Calcutta had a Holy Hour each day and all members of her Missionaries of Charity followed her example. The Holy Hour has been practiced by saints such as Gemma Galgani and Faustina Kowalska.

To keep watch with Jesus for one hour is to pray for one hour! For Jesus himself prayed during that above mentioned time frame.

When asked to teach his disciples how to pray, Jesus responds by saying 'when ye pray' but does not specify when, or how often or how long, Luke 11:1.

He then gives an example of prayer (and advises not to use it as mere repetition for he warns against such a thing elsewhere Matthew 6:7) and the example takes but a minute or two to actually voice.

There are many examples of prayer in scripture but I have never yet found a rule or a requirement about time or frequency.

And it came to pass, that, as he was praying in a certain place, when he ceased, one of his disciples said unto him, Lord, teach us to pray, as John also taught his disciples. And he said unto them, When ye pray, say, Our Father which art in heaven, Hallowed be thy name. Thy kingdom come. Thy will be done, as in heaven, so in earth. Give us day by day our daily bread. And forgive us our sins; for we also forgive every one that is indebted to us. And lead us not into temptation; but deliver us from evil. [Luke 11:1-4 KJV]

Daniel (for example) used to pray three times a day but this was only discovered when he was put under constant surveillance so that some fault might be discovered whereby he could be prosecuted as prayer was forbidden at the time to any but the king, see Daniel 6:10-28.

But Daniel never commands anybody else to pray three times a day. It was just what he chose to do. Similar examples may be found in the psalms where psalmists promise (to God) to pray or give thanks. But this is between them and God himself. They do not demand it of others.

In the garden of Gethsemane, Jesus was in an extremity. He wanted company and support. But the disciples were weary and could not stay awake to watch during the hours of the night.

In the end God, the Father, sent an angel to strengthen Jesus in answer to his prayer, see Luke 22:43.