New American Standard Bible (NASB)
Numbers 8
24 "This is what applies to the Levites: from twenty-five years old and upward they shall enter to perform service in the work of the tent of meeting.
25 But at the age of fifty years they shall retire from service in the work and not work any more.
26 They may, however, assist their brothers in the tent of meeting, to keep an obligation, but they themselves shall do no work. Thus you shall deal with the Levites concerning their obligations."
Numbers 9
1 Thus the Lord spoke to Moses in the wilderness of Sinai, in the first month of the second year after they had come out of the land of Egypt, saying,
2 "Now, let the sons of Israel observe the Passover at its appointed time.
3 On the fourteenth day of this month, at twilight, you shall observe it at its appointed time; you shall observe it according to all its statutes and according to all its ordinances."
4 So Moses told the sons of Israel to observe the Passover.
5 They observed the Passover in the first month, on the fourteenth day of the month, at twilight, in the wilderness of Sinai; according to all that the Lord had commanded Moses, so the sons of Israel did.
6 But there were some men who were unclean because of the dead person, so that they could not observe Passover on that day; so they came before Moses and Aaron on that day.
7 Those men said to him, "Though we are unclean because of the dead person, why are we restrained from presenting the offering of the Lord at its appointed time among the sons of Israel?"
8 Moses therefore said to them, "Wait, and I will listen to what the Lord will command concerning you."