Christ established His Church on earth so that sinners might receive His gifts of Word and Sacrament. Put another way, the Church exists to give sinners Jesus.
The last thing we want to do is to put a barrier between Jesus and His people. But this can happen in a variety of ways, for example, by not coming to church, neglecting God’s Word and prayer at home, and living a willful, deliberately sinful life. Unfortunately, even churches can be guilty of putting a barrier between Jesus and His children (no doubt unintentionally). This often happens when it comes to the practice of the Lord’s Supper, either by admitting those who are not yet ready (open communion), or by denying the sacrament to those who are ready, but not yet a certain age.
What makes one worthy of the Sacrament is that good Lutheran teaching—faith alone. Luther himself says so in the Small Catechism. Who receives this Sacrament worthily? That person is truly worthy and well prepared who has faith in these words: “Given and shed for you for the forgiveness of sins.” To add anything else to this (such as a confirmation requirement) is to, like the scribes and Pharisees, teach as doctrines the commandments of men (Matthew 15:9).
We dare not think that somehow our faith is any better than anyone else’s, for faith is a gift, something the Holy Spirit gives equally to all of His children when and where He wills, young and old alike. Far from being unable to believe, our Lord praises the faith of infants as exemplary, for “whoever does not receive the kingdom of God like an infant shall not enter it,” (Mark 10:15). If anything, the more we grow, the less trusting we become and the more we begin to question and doubt our faith. Infants, on the other hand, are totally helpless and dependent, who rely fully on their parents to meet all of their needs. Our Lord wants us to believe in exactly the same way: not trusting in our own reason or strength, but as helpless and dependent newborn babes, fully relying on God to meet our every need in Christ Jesus.
The Lord’s Supper is a gift, and if receiving it depended on our ability to understand it, nobody—pastors included—would ever be able to receive it.
Children and adults may believe and so be worthy of the Sacrament from the time of Baptism, but this does not necessarily mean they are ready to commune. What makes a worthy child of God ready to receive the Sacrament? They must be taught to confess the faith. The Bible teaches that we ought to have unity in the faith and in our lives before we commune together (see Matthew 5:23-24, 1 Corinthians 10:16-17, and 1 Corinthians 11:26). This is why we do not commune with those who have not yet been instructed (such as infants or non-Christians) or hold to a confession that differs from ours (those who belong to another denomination).
Learning to confess the Christian faith happens both in the home and at church. This happens in the Divine Service, bible class, catechesis in the home, and also during formal confirmation classes. This is what makes confirmation valuable; it’s another opportunity to learn about Jesus and grow in the faith. But this is a lifelong process—from cradle to the grave. You never can learn too much about Jesus, nor do you ever “graduate” from growing in Christ. Christian catechesis does not end with confirmation; it ends with death.
So at what point in this lifelong study of God’s Word is someone ready to receive the Sacrament? Following the lead of Martin Luther, The Lutheran Church—Missouri Synod has identified basic catechesis in the chief parts of the Small Catechism as a primary requirement and has included a “Rite of First Communion Prior to Confirmation” in The Lutheran Service Book: Agenda. It says:
Candidates for admission to the Lord’s Supper have learned the Ten Commandments, the Creed, and the Lord’s Prayer. They have received careful instruction in the Gospel and Sacraments. Confessing their sin and trusting in their savior, they desire to receive the Lord’s Supper for the forgiveness of sins and the strengthening of their faith in Christ and their love toward others.
Once this takes place, worthy children of God—regardless of age—are ready to commune. Anybody who desires to receive the sacrament ought to be welcome to the Lord’s Table after a period of basic catechesis (instruction) and examination/absolution by the pastor (according to the practice described in Augsburg Confession, article XXIV).
 While the Lord’s Supper is not the context here, the principle nevertheless applies. The Sacrament of the Altar is, among other things, an expression of our unity, both in terms of our doctrine and our lives.
 Lutheran Service Book: Agenda, 25.