That the Lord’s supper ought not to be celebrated privately, by one person alone may be proven;
1. Because it is a communion, and is the sign of our communion with Christ: but a private supper is no communion.
2. Because it is a solemn thanksgiving; and we ought all to render thanks unto God. Hence he who regards himself as unworthy to communicate with others, declares that he is not fit to give thanks unto God.
3. Because Christ, with all his benefits, is not the property of one, but belongs to all in common. A private communion would, however, make a private good out of that which is common.
4. Because Christ admitted all his disciples, yea even Judas, from which it is easy to see that a private communion is contrary to the appointment of Christ.
5. That some neglect the communion or defer it even until death, arises no doubt from some wrong notion, or influence, either because they will not commune with others, or because they think that they are not worthy. But all who believe that they are delivered from eternal condemnation by the death of Christ, and desire to advance in holiness, are worthy.
Briefly, when the Lord’s supper is observed by one person alone it is done contrary to the design, name, institution, and nature of the sacrament.
Ursinus, Zacharias, and G. W. Williard. The Commentary of Dr. Zacharias Ursinus on the Heidelberg Catechism. (Cincinnati, OH: Elm Street Printing Company, 1888).