From New Living Translation:

Numbers 8:23-26: "The LORD also instructed Moses, 'This is the rule the Levites must follow: they must begin serving in the Tabernacle at the age of twenty-five, and they must retire at the age of fifty. After retirement they may assist their fellow Levites by performing guard duty at the Tabernacle, but they may not officiate in the service. This is how you will assign duties to the Levites.'"

As far as I am aware, this is the only place in Scripture where retirement is directly referenced.

Generally, "retirement" as it is practiced in this generation is out of sync with Scripture. Scaling down to ability and responsibility is more the principle.

Prioritization of a carefree lifestyle of self-seeking pleasure for this station of life is not biblical (any more than at any other stage of life). Older people have much to offer God and their fellow man, which is a key reason for life itself.

That doesn't mean older people will not have different responsibilities or a different amount of responsibility. It doesn't mean God will not give them plenty of time to rest, (e.g. the Sabbath), learn, travel or enjoy His Creation. In reality, He does this at every stage of life and hopefully, we can, by His grace, better understand that as we mature.

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Scott
PCA
North Carolina