Sean Lucas of Covenant Theological Seminary has posted an excellent article on his blog on the essential incompatibility of Sola Scriptura and the Regulative Principle with the practice of observing invented Holy Days in the worship of church.
Lucas notes in his article, “While I am aware that some would make a biblical argument for using the church calendar based on the OT development of sacrifical feast days (an argument that is not convincing to me), I would suggest that what we have for our place in the redemptive, biblical drama is actually a rhythym of 52 feasts days a year–the Lord’s Day in which Word, Sacraments, and prayer constitute the heart of the church’s “calendar.” “
His comment regarding the specious argument that the commanded Old Testament holy days provide the pretext for the invention of New Testament Holy Days reminded me of the comments of several Puritan divines, such as Thomas Watson, who dealt with the same argument as it was advanced by Roman Catholics and Anglicans in their own day. Watson answered:
“The ceremonies of the law, which God himself ordained, are now abrogated, and out of date. Christ the substance being come, the shadows fly away; and therefore the apostle calls the legal ceremonies carnal rites. Heb 9: 10. If we may not use those Jewish ceremonies which God once appointed, then not those which he never appointed.”
Building Old School Churches 
Interesting. I was thinking that whatever one’s thoughts were on using the calendar that this article was extremely weak and convoluted. His next day follow-up seemed to be necessary but did not clarify anything.
Hi Brian,
In reading Lucas’ article, we have to face certain facts. Sean is a highly visible representative of our denominational seminary, and the vast majority of our churches (80%+) do in fact observe holy days, so there is only so much he can say. The fact that he said it all, and took the OSP position against the modern practice was fairly bold and I can understand his use of language that was far more cautious than I would use. You’ll note that in no time at all the FV men, Anglo-Catholics, and high church liturgists in the PCA were jumping all over him for what he did say in the first place.
Also, I appreciated it for what it was, a simple blog article that hit most of the essentials – not a highly polished theological essay. In that sense, I thought it was great. Would that the majority of profs at CTS agreed with him about the implications of Sola Scriptura and the RPW for our faith and practice.
Thank you Andrew. I have much respect for Sean’s boldness in speaking on this subject. Honestly, I am not sure where most of the men at CTS stand on these subjects. I have seen posts recently by students at CTS advocating some form of Ash Wednesday observance, whichs seems ill advised to me, and I wonder where they are getting their inspiration.