1 Chronicles 23:24

From the age of twenty years - The Levites had hitherto not entered upon their regular functions until the age of thirty 1 Chronicles 23:3. Certain lighter duties were by the Law imposed on them at the age of twenty-five Numbers 8:24; but it was not until they were five years older that they became liable to the full service of the sanctuary. David appears now to have made a change. By his “last words” 1 Chronicles 23:27 the time for the Levites to enter on the full duties of their office was advanced from thirty to twenty years. This change was based upon the lighter character of the labors imposed on them now that the ark had ceased to be carried from place to place and obtained a permanent habitation 1 Chronicles 23:26. The limit of age continued in after times where David had fixed it (see Ezra 3:8).