Great question! However, if it's answers you are looking for, keep looking... all I have are conjectures and inklings.
An old friend of mine (emphasis on old) always used to tell me that the concept of retirement is not discussed anywhere in the Bible, therefore retirement is not Biblical. Hm. That never seemed quite right to me, so I have mulled it over as the decades have rolled along, and I still don't think he was right.
And never mind that as of this writing I am 5 weeks away from retirement! Of course I have a vested interest in a counter-argument to his thesis! But stay with me here as we look at a few passages, and we'll see if this idea makes sense.
As a preface to that review, though, let me just say that as of the 2nd week of July, 2021, I will have been employed full-time for 45 years. (46 years elapsed time since my first full-time job in July of 1975, but one of those years was spent in college finishing up my Bachelors degree, so that doesn't count as time employed.) The first 7 1/2 years were spent in various property & casualty insurance jobs, another 34 years in various actuarial jobs within that same sector and the last 3 1/2 in the banking sector.
"But, you're only 65", you say. "Shouldn't you be working longer?"
And I say, longer than what? If a young person today goes from high school to college and on to grad school, coming out with some sort of professional designation like a CPA, for example, they would be about 25 when entering the marketplace, right? If they worked until age 70, that would be 45 years of full-time work, and a ripe old age to retire. Seems about right. So what if I started working at 19 and got my Masters and my professional designation along the way while working full-time. So what? It's non-linear, yes, but it amounts to 45 years of work nonetheless.
In the Old Testament, 40 years was the number of a generation, a number representing fullness of time. Judges and Kings were frequently described as ruling for 40 years, and then another ruler took over. Sometimes they would rule a little longer, which was a sign of God's blessing on them. So I'm good with 45!
And lest you think that lifespans have changed significantly since then, think again. Here's Psalm 90:10:
The days of our lives are seventy years;
And if by reason of strength they are eighty years,
Yet their boast is only labor and sorrow;
For it is soon cut off, and we fly away.
Last I looked, the current actuarial tables (pre-COVID) list a global life expectancy of about 72.8 years (with post-COVID Americans sitting at about 77.5; slightly longer for females, less for males). So it seems that the ancient Israelites with their Kosher dietary laws had a fairly modern expectation of what a lifespan would be. Plus, recent research shows that increased life expectancy mostly comes from infant mortality going down. We all still fade out in our 70s & 80s.
In Leviticus, when it came to valuing workers for the purpose of temple taxes, men not in their prime years (20-60) were expected to be less productive when it comes to manual labor, and so were assessed less:
3 if your valuation is of a male from twenty years old up to sixty years old, then your valuation shall be fifty shekels of silver, according to the shekel of the sanctuary. 4 If it is a female, then your valuation shall be thirty shekels; 5 and if from five years old up to twenty years old, then your valuation for a male shall be twenty shekels, and for a female ten shekels; 6 and if from a month old up to five years old, then your valuation for a male shall be five shekels of silver, and for a female your valuation shall be three shekels of silver; 7 and if from sixty years old and above, if it is a male, then your valuation shall be fifteen shekels, and for a female ten shekels.
We could certainly digress into a discussion of the difference in valuation due to gender (no doubt recognizing the difference in body strength when doing manual labor), but that's not the point here - this is a discussion about valuation based on age. And what you notice is that, taking an adult male for the 40 years between ages 20 and 60 as the baseline for full productivity, you get the following:
Age Range Valuation Percentage
The older males were seen as less productive for manual labor than youths were, implying that 70% less work would be done once a worker was past 60. (It should be noted that females had less of an age penalty percentage applied to their valuation as workers, perhaps because of the nature of the labor they typically took on. But again that's beyond the scope of this discussion.)
Personally, I find it interesting that the US Military expects retirement (even in the Reserves) to occur at age 60 (unless one is a flag officer, and then that limit extends a few more years).
In I Timothy 5:9, we also read that "no widow is to be enrolled on the list for support unless she is at least sixty years old ..." with the implication that older women will have a harder time supporting themselves, as their capacity for work is diminished.
So age 60 (out of 70-80 total) seems to be a good time to dial things back. We wind up then, with 20 years of growing up, 40 years of productive labor, and another 10-20 years of winding down.
But another example is even more restrictive, and this one is from active service in the Temple, no less. Give a listen to this passage:
Numbers 8:23 The Lord spoke to Moses: 24 “In regard to the Levites: From 25 years old or more, a man enters the service in the work at the tent of meeting. 25 But at 50 years old he is to retire from his service in the work and no longer serve. 26 He may assist his brothers to fulfill responsibilities at the tent of meeting, but he must not do the work. This is how you are to deal with the Levites regarding their duties.”
Wow. Okay, so mandatory retirement at age 50? And only a 25 year work span instead of 40 years? No explanation here is given - it just is what it is, but we can certainly assume a little longer training period before entering the priesthood might be needed. But the compensating factor is that the older priest, the retired guy, is encouraged to assist his brothers. Maybe this is the model for service in the Kingdom of God - you give the younger guys a little more time to mature first and you allow the older guys to ease out of the workload a little earlier, but still keep their hands in and continue to be useful as they age.
After all, aging is no joke. As they say, it's not for sissies. And if there ever was a passage that makes that clear it's Ecclesiastes 12:1-7. To wit:
Remember also your Creator in the days of your youth, before the evil days come and the years draw near of which you will say, “I have no pleasure in them”; before the sun and the light and the moon and the stars are darkened and the clouds return after the rain, in the day when the keepers of the house tremble, and the strong men are bent, and the grinders cease because they are few, and those who look through the windows are dimmed, and the doors on the street are shut—when the sound of the grinding is low, and one rises up at the sound of a bird, and all the daughters of song are brought low— they are afraid also of what is high, and terrors are in the way; the almond tree blossoms, the grasshopper drags itself along, and desire fails, because man is going to his eternal home, and the mourners go about the streets— before the silver cord is snapped, or the golden bowl is broken, or the pitcher is shattered at the fountain, or the wheel broken at the cistern, and the dust returns to the earth as it was, and the spirit returns to God who gave it.
Hebrews 8:13 tells us clearly that "what is obsolete and outdated will soon disappear". In the marketplace that is certainly a truism! And I for one am ready to stop working for a paycheck.
However, that doesn't mean for me a life of self-indulgence and leisure. After all, if I am a servant of the Most High God, He who never sleeps or slumbers, then there is no "off switch" for my service. I never punch out for the day, I am always on call, always a servant of God, even when I'm asleep. I may no longer have an earthly master to serve, but I do have a Heavenly One, and I must apply myself to His service with whatever zeal my body and mind allow. From that work I will not retire, and the paycheck for it... is eternal!
