The Regulative Principle of Worship (RPW) is the Reformed conviction that God, not man, determines how He is to be worshipped. Scripture contains the commands, examples, and inferences by which we know what pleases God in corporate worship; anything not so authorized is forbidden. The principle is grounded in several biblical examples: (1) Nadab and Abihu offered "strange fire" before the LORD, "which He had not commanded them," and they were struck dead (Leviticus 10:1-2); (2) Uzzah touched the ark and was struck dead for violating God's prescribed method (2 Samuel 6:6-7); (3) Jesus condemned the Pharisees for "teaching as doctrines the commandments of men" (Matthew 15:9). The opposite view, the Normative Principle, holds that whatever is not forbidden is permitted — this is the Lutheran and Anglican position. The RPW is the Reformed and Presbyterian position, and it sharply limits worship to preaching the Word, reading the Word, singing psalms or biblical songs, praying, administering the sacraments, and in some traditions, taking vows and giving offerings. The RPW is not legalism; it is a posture of humble reception: we come to God on His terms, not ours. The question is not "What do I want to do in worship?" but "What has God commanded?"