Numbers 8:25,26

From the age of fifty they shall cease waiting Shall be excused from carrying the parts and vessels of the tabernacle, and all the toilsome duties of the service, and shall only give advice and direction, and assist in lesser and easier works. How merciful and full of compassion are the laws of God! When his servants became advanced in years in his service, they were not required to do the same work which they did when younger. But doubtless many of them, who were of age to take the benefit of this kind provision made for them, would show their love to God by still exerting in some way their last remains of strength in his service. And surely happy are they who, by the blessing of God on a temperate life, are preserved to old age, with strength to labour in His service who gave them being, and died to redeem them.