2. Speak unto all the congregation of the children of Israel--Many of the laws enumerated in this chapter had been previously announced. As they were, however, of a general application, not suited to particular classes, but to the nation at large, so Moses seems, according to divine instructions, to have rehearsed them, perhaps on different occasions and to successive divisions of the people, till "all the congregation of the children of Israel" were taught to know them. The will of God in the Old as well as the New Testament Church was not locked up in the repositories of an unknown tongue, but communicated plainly and openly to the people.
      Ye shall be holy: for I . . . am holy--Separated from the world, the people of God were required to be holy, for His character, His laws, and service were holy. (See 1Pe 1:15).

JFB.