There is definitely nothing in the Scriptures that deals with a "first communion." First Communion is a part of training children in Roman Catholic teaching, and it has been developed as one of their seven sacraments. In Roman Catholic theology, a sacrament is an act that someone does to get God’s grace or favor. Before a child has any understanding of sin, he or she is baptized, the first sacrament in the RCC system. Then he goes through a series of catechism lessons, after which he goes to his first Confession. This is called “reconciliation” or “penance” and involves going to a priest, confessing sins to him and performing whatever penance or prayers and deeds the priest prescribes. Only after that may a Roman Catholic begin taking Communion.
In contrast to this, the Scriptures tell us, "For there is one God and one mediator between God and men, the man Christ Jesus" (1 Timothy 2:5). We are not called to confess our sins to any man to have them forgiven, but to pray and confess to God. It is only through Jesus Christ that we find full and free forgiveness. Titus 3:5-6 is only one of many passages that identify Jesus as the method of forgiveness, not some religious ritual.
We learn about the Lord’s Table in 1 Corinthians 11:23-34. Communion is for believers in Jesus Christ, and it is to be observed with a mindset of humility. The Corinthian church was abusing this service, so Paul under the authority of the Spirit of God pens for us the attitude we need to bring to this memorial service. It is a memorial service for Jesus Christ, who died once for all. He does not need to be re-sacrificed, as the Catholic Mass attempts to do. Jesus Christ already died, was buried, and rose again from the dead. As we take the bread and the cup we “proclaim the Lord’s death until He comes" (1 Corinthians 11:26). He is alive today, and we are asked to remember each time we participate in the Lord’s Table that Jesus is alive and coming again!
So, there is no biblical foundation for the man-made rituals of "First Confession" or "First Communion" such as the Roman Catholic Church has developed. There is, however, an important truth that God wants us all to know—Jesus Christ did die on the cross for our sins, and He wants us to come to Him to find forgiveness. Also, He does want us to participate in the Lord’s Table once we have come to Him and to remember His once-for-all act of love on the cross at Calvary.
If there is a proper understanding of communion, is there anything wrong or unbiblical about celebrating a child’s first communion? No, there is not. In fact, a person’s first participation in communion is a wonderful thing, well worth celebrating. When a person places personal faith in Jesus Christ, and then, through communion, worships the Savior by remembering His death and shed blood, surely that would be appropriate to recognize and celebrate.