Here’s what the Bible has to say about how people should be treated (or how they were treated) based on their age.
God told his people to consecrate every firstborn male to him, whether they were humans or animals, and they would belong to him. I can’t tell if that’s a good thing or a bad thing for the firstborn. It could mean they’re declared sacred, and therefore entitled to respect. It could also mean they have to be dedicated to the service of God, which sounds a lot like forced labor.
It could even mean that God wants his people to make sacrifices of their firstborn sons. God says to do the same thing with your firstborn sons that you would do with firstborn animals, which are to be killed when they’re given to God. But it also says some animals and sons can be redeemed, and don’t have to be killed.
Whatever it means, God apparently decided the Levites would replace the firstborn males in that role. So it doesn’t even really matter what would have happened to the firstborn. Or does it? A thousand years later, the Jews still thought they needed to bring the firstborn of their sons and livestock to the house of God…
There’s a passage where God tells exactly how much he thinks different kinds of people are worth. For instance, he thinks males are always worth more than females of the same age. As for age differences in value, God says 20-60-year-olds are worth the most. People between five and twenty are less valuable, and people over 60 are worth less than that. Children one month to five years old are valued even less. And babies under a month old aren’t even worth mentioning.
God assigned duties at the tent of meeting to male Levites who were 25 or older. But he didn’t allow them to work anymore after they reached 50.
The psalmist who wrote the longest chapter in the Bible claimed to have more understanding than the elders.
God mentioned that when Babylon attacked his people, they showed no mercy even to the aged. I can’t tell if he approves of that, though. That chapter is generally disapproving of Babylon, but punishing his people is exactly what God wanted Babylon to do…
Paul says you shouldn’t be harsh when you tell older men what to do.
Against younger people
The law of Moses demands that people show respect for the elderly and stand up in their presence. Paul also said younger people need to submit to their elders.
Elihu was afraid to speak up at first, thinking it was best to listen to older and wiser people. But after Job and his three friends had been arguing for 29 chapters and had gotten nowhere, Elihu decided he could be at least as wise as them. So he gave his own six-chapter-long speech, but everyone completely ignored him.
When God had Moses count the Levites, he specifically had him exclude anyone less than a month old.
God’s law says a man has to give his firstborn son twice the inheritance a younger son would get, whether he wants to or not.
The law says it’s okay to take young birds out of a nest, but it’s not okay to take the mother.
Saul didn’t think David would be able to fight Goliath, because David was “only a young man“.1 Goliath didn’t think much of him either.
Solomon thought beating your children with a rod was a loving thing to do, and would make them wiser. He thought not beating children was a disgrace, and the only possible reason anyone would refuse to do it was that they hated their children. Proverbs insists that if you beat children, they definitely won’t die.
King Rehoboam consulted both old and young people to help him decide whether he should give the people what they were asking for. The Bible says he ended up following the advice of the young people, and he lost most of his kingdom as a result.
Hezekiah had his people donate heaps of food “to the Lord”, which actually all went to the priests and Levites. Even though the priests and Levites had more than they needed, they didn’t distribute food among themselves to anyone below a certain minimum age.
Isaiah thought children weren’t good at counting. Paul said underage people are no different from slaves. When “Matthew” estimates how many people Jesus fed, he says how many men there were, and only mentions as an afterthought that there were also women and children. Jesus thought people didn’t have enough respect for children. But even he equated being the youngest with not being so great.
Paul told his followers not to care for any widows who were under 60.
Against older people
Joseph thought his firstborn son should be blessed the most. But his father Jacob insisted on giving the better blessing to Joseph’s younger son. Similarly, Hosah the Merarite treated one of his own younger sons as if he was the firstborn.
To convince Pharaoh to let his people go, God killed every firstborn in Egypt.
There’s an oddly specific biblical law that says you can’t cook a young goat in its mother’s milk. There’s no rule against cooking an older goat in its mother’s milk,2 but don’t do it to a young goat!
When Moses told the Israelites to attack nations that weren’t even anywhere near the land they were trying to take over, he said they should offer to enslave everyone in those nations. If a nation refused this “offer of peace”, then the Israelites would kill all the men, and only enslave all the women and children.
Boaz was surprised that Ruth showed interest in a man as old as him. He expected young women like her to run after the younger men.
Nobody’s allowed to work on the Sabbath, including children.
If God’s people didn’t obey him, he threatened to bring a fierce nation against them that would have no pity on the old or the young. God did eventually send the king of Babylon to conquer the kingdom of Judah. That king had most of the people killed, not sparing the young or the elderly, and took the rest captive. Haman later plotted to kill all the Jews in Persia, young and old, women and children.
After Joshua’s army made the walls of Jericho collapse, they charged in and destroyed every living thing in the city, young and old. Later, God told Saul to totally destroy the Amalekites, putting to death men and women, children and infants. Equality!
Saul had a shepherd kill all the men, women, children and infants in a whole town, because one guy in that town had helped Saul’s enemy without knowing he was Saul’s enemy. Isaiah said God was going to send the Medes to destroy Babylon, and they would have no mercy on children and infants.
The Levites divided… something (duties?) among themselves impartially, without favoring the family of an older brother over the family of a younger brother. (Would they normally?)
God once said he was going to let children rule over Judah… to punish the people. Though having children for rulers isn’t always portrayed as a bad thing.