Here is a great article by Jaquelle Crowe on desiringgod.org:
She opens the article by saying:
We like people who are like us. Beginning as children, we’re corralled by different categories and compartmentalization. Age may be the biggest. From grade school to Sunday school to the workplace, we tend to intuitively gravitate to those who are the same age as us.
Many churches (surely unintentionally) feed this anti-intergenerational message: children go here for Sunday school, teens go here for youth group, separate Bible studies and classes for college, career, parents, and seniors. Quietly and subtly we come to believe that our friends should exclusively be from our generation.
Yet while having friends of the same age is normal and natural, we miss something special when we don’t have any friends who are of different ages than us, particularly in Christian community. Christians share a bond and identity that trumps everything else — job, race, and most definitely age. If there’s no longer Jew nor Greek, slave nor free, male nor female, there should be neither old nor young (Galatians 3:28).
Age should not build walls. Jesus should tear them down. When we put aside our preference for people just like us, we broadcast the beauty of our shared union with Christ.
And intergenerational friendship is not just beautiful, but necessary. We need intergenerational friendship. We need the balance, perspective, and experience of people who are walking through different stages of life than us (1 Timothy 4:12; 5:1–2; Titus 2:3–5). Teenagers, you need older Christians. Seniors, you need teenagers. Young moms, you need empty-nesters. Empty-nesters, you need twenty-somethings. We all need each other.