47-1. Since the Holy Scriptures are the only infallible rule of faith and practice, the principles of public worship must be derived from the Bible, and from no other source.
The Scriptures forbid the worshipping of God by images, or in any other way not appointed in His Word, and requires the receiving, observing, and keeping pure and entire all such religious worship and ordinances as God hath appointed in His Word (WSC 51, 50).

[DIGEST: What we have now as chapter 47 was not part of either the Proposed Book of Church Order (1973) or the Book of Church Order as adopted by the first General Assembly later that same year. Rather, this chapter, with its nine paragraphs, dates to 1975 when this text was presented by the Constitutional Documents Committee, as part of its proposed revision of the Directory. [M3GA, 3-15, pp. 55-56] This chapter, originally numbered as chapter 48, presents entirely new text not previously part of any prior Presbyterian Book of Church Order. The chapter was renumbered as chapter 47 when the original chapters 8 and 9 were merged in 1980. No changes to paragraph 47-1 have been made since adoption in 1975, other than the editorial addition of the parenthetical Shorter Catechism reference at the end of the verse.

ANTECEDENT TEXTS:
1975, 48-1, [M14GA, p. 339]
Since the Holy Scriptures are the only infallible rule of faith and practice, the principles of public worship must be derived from the Bible, and from no other source. The Scriptures forbid the worshipping of God by images, or in any other way not appointed in His Word, and require the receiving, observing, and keeping pure and entire all such religious worship and ordinances as God has appointed in His Word (WSC 50, 51).

No comparable text in any of the following editions:
1. PCA 1973, Adopted text, as printed in the Minutes of General Assembly
2. Continuing Presbyterian Church 1973, Proposed text
3. PCUS 1933
4. PCUS 1925
5. PCUS 1894

COMMENTARY:
Morton H. Smith, Commentary on the Book of Church Order, 6th edition, 2007, p. 395-396.
Here we find a restatement of the regulative principle of worship which is found in the Confession and Catechisms, namely, that all acts of public worship must be derived from the Bible. The second paragraph is a recasting of the Shorter Catechism questions as indicated.
This principle, simply stated is that we are to include in worship only what God's Word teaches. This principle receives a four-fold emphasis in the Confession and Catechisms (WCF II, 2, XXI, 1, LC 108-109, and SC 50-51, and is again restated here as the basic principle of the Directory for Worship. In the light of the variety of , approaches to worship in the Church today, this emphasis is needed.
This view of worship was one of the distinguishing marks of Reformed worship over against Rome and Lutheranism. The worship of Rome reflects the traditions of the Church, and has lost the simplicity of New Testament worship. The Lutheran approach is that anything not forbidden in the Bible may be permitted. The Reformed view is to include only what is specifically warranted by Scripture. As the Shorter Catechism says it, "The second commandment forbiddeth the worshipping of God by images, or any other way not appointed in his word."[1]
One point that needs to be clarified before entering into the guidelines given in the Directory for Worship is the sharp distinction that must be made between the Old Testament and the New Testament worship. The worship of the Old Testament differs from that of the New in that the Old was ceremonial, looking forward to the coming of the Messiah through the use of the sacrificial system. The New Testament, on the other hand, reflects the fact that the Messiah has come. Preparation for this simpler form of worship came in the development of the synagogue, especially during the exile and the subsequent dispersion of the Jews. When we seek to know what the Bible teaches about Christian worship, we should not look to the ceremonial worship of the Old Testament, but rather to the practice of the New Testament Church. When this is recognized, we can understand what lies behind the Directory for Worship, which rests on the Directory adopted by the Westminster Divines. If this principle is kept in view, it will guard us from falling into serious errors in our worship practices.