Here is the position that most RP churches hold to:
“When coming into a service of our church, a visitor may find some things in the service a little unusual. We want to worship God in those ways He has appointed, and no other. As a result, our worship normally consists of the reading and preaching of the Word of God, prayer and the singing of psalms without musical accompaniment. Occasionally, also, the sacraments of baptism and the Lord’s Supper are observed. We find no Biblical basis for going beyond these parts of worship.”
The RP church is close, but still falls short in important ways.
Why is baptism and the Lord’s Supper called a “sacrament” in the RP church? Because they are still hanging on to something learned from the Roman Catholic church. The idea is that in infant baptism and in the Lord’s Supper there is a special work of grace that’s imparted for the cleansing of the soul.
First to the point of baptism, it isn’t true that infant baptism imparts any grace as the infant is not lost, has committed no sin, and couldn’t repent even if it had sin. The baptism is observed whenever a lost person wishes to be saved. It is not something scheduled “occasionally” by the church. According to the need of the soul, baptism is received by a sinner who wishes to be saved by God’s grace. The RP church relies upon the teachings of John Calvin and it regularly consults the Westminster Confession of Faith. Therefore it accepts that every soul is conceived in a corrupted, lost, and with a complete inability to understand or do anything towards God. RP teaches that the few a selected for salvation by divine decree and that faith and acknowledgement of Jesus Christ can only follow God first regenerating the heart. To them, salvation comes first, then the faith, confession, repentance and the life as a disciple. This is completely false and it corrupts the doctrines of grace, faith, sin, and salvation. That’s point number one.
Secondly, the Lord’s Supper was a first day of the week observance. Every first day of the week is the biblical example and the historical position. Christ was raised on the first day of the week and Christians met on the first day of the week to assemble and worship and to be edified through hearing the Word of God, through prayer and singing, and through partaking of the Lord’s Supper for remembering the cross, and through the giving in the collection. All of these were and are done on every first day of the week. Romans Catholics and many Presbyterians practice a “closed communion” because it is a sacrament to them, imparting a saving grace in the eating and drinking, and therefore is not offered to those who are not yet confirmed to be a part of the church. In the church of Christ, we hold that the Lord’s Supper, as with baptism, should be received soberly and thoughtfully in faith so that it is not partaken of in an unworthy manner (1 Cor 11:23ff), but just as a visitor to the church may participate in other areas of worship, the church does not hinder the visitor from partaking of the emblems which are a remembering of the Lord’s death on the cross.
Thirdly, the RP church is sound in their exclusion of the musical instrument from the worship of God. The problem they have is that they only allow the singing of the Old Testament Psalms. They will not sing songs written by uninspired men. But this is an error of judgment. A song written by a man is permitted under the Apostle’s admonition in Ephesians and in Colossians to “sing Psalms, hymns, and spiritual songs.” I agree we need to sing more of the Psalms, but the spiritual songs are written by men and they are just as acceptable as a sermon written by a man. We do not only read the Scriptures. We expound upon them which is just as Biblical. And so a song, written by a man, if all of the content is Biblically sound, is just as acceptable. So this third point on the singing of only the Psalms is too strict and a man-made rule of the RP church.
The RP church is closer to the truth than many denominations. But if you are part of this denomination, consider that Baptism was in the Scriptures something to be administered to adult sinners (adult age in the Scriptures is somewhere around 12 or 13 and upward). If you are part of the Reformed Presbyterian church, then come to the church of Christ where the Lord’s Supper is observed every first day of the week, Acts 20:7. “On the first day of the week” is the pattern to follow. As in the Old Law, every last day of the week, the Sabbath was observed. The Law didn’t need to specific “every” Sabbath when it said to “remember the Sabbath day to keep it holy”. It meant “every” one of them that comes every 7 days. The first century church believed this and history records that every week it was observed.