Certain Biblical paragraphs are stated in a Theme-Development form. In other words a broad general idea is stated first followed by the development of this broad general theme in specific details. The Theme-Detail form creates a unified paragraph and consequently the law only applies to the enumerated details but not to other cases. Today's example illustrates this as shown below.

Verse Nu03-06a is written in a General-Detail form:
• General: Bring the tribe of Levi near, and set them before Aaron the priest, that
• Detail: They may minister unto him.
Notice the word that which indicates the transition in the general-detail form. The Rabbi Ishmael style rules require that such a sentence be interpreted restrictively. Levites help the priests only by serving and ministering to them (e.g. by singing songs of praise during the Temple service); but not e.g. by offering sacrifices. Rashi derives this restrictive interpretation from the Detail clause - that they may minister unto him - which restricts the general clause Bring the tribe of Levi near and set them before Aaron the priest. Here is still another way of looking at it. The general clause by itself means that the Levites help Priests in all matters, including offering sacrifices, singing songs of praise etc. However because the general clause is followed by a detailed clause I therefore interpret the verse to mean that only by ministering - that is singing songs of praise - do the Levites serve the Priests.

Advanced Rashi: Actually the word minister is a bit more general. Besides singing Psalms during the Temple service the Levites assist in a variety of other ways. For example, the Levites assisted with ritual slaughter of the sacrifices. In this posting we have only touched on the basic idea that the assistance the Levites give the Priests is restricted. We have not fully explored how it is restricted. A more thorough analysis would require reviewing many Biblical texts where the Levite methods of assisting the Priests are listed.