Mark 13:12
Now the brother shall betray the brother to death, and the father the son; and children shall rise up against their parents, and shall cause them to be put to death. Now the brother shall betray the brother to death, and the father the son; and children shall rise up against their parents, and shall cause them to be put to death.
On the Mount of Olives Jesus answered Peter and James and John and Andrew when they asked when the judgment on the temple would happen and what the sign would be when all things were to be fulfilled, and this warning about household betrayal was part of that answer. That discourse concerns both the destruction of Jerusalem and the end of the world, joining the two crises so that words spoken about Jerusalem's destruction also reach forward to the final events of earth's history, giving the warning both a historical and a final application. It predicts that followers will face deadly persecution for Christ's sake and for His name within their own households, where brother will betray brother to death, father will betray son and child, and children will rise up against parents and cause them to be put to death, alongside being delivered to councils and rulers and authorities to testify and being hated by all for His name.
The division comes through loyalty to Christ when unbelieving relatives who reject Him oppose, persecute, and even deliver to death family members who serve Him, resenting their faith and happiness, so that obeying God's commandments can bring scorn, ridicule, hatred, and unavoidable conflict at home. Religious disagreement, especially over the interpretation of Scripture, can stir human passions and bitterness that sever bonds of friendship and family and become the occasion for betrayal, reflecting the same spirit that condemned Christ. In a future crisis when Satan's spirit rules human hearts, human relationships cannot be trusted when such passions hold sway.
The betrayal will be fulfilled in blind zeal when Satanic agencies unite with the professed Christian world in opposing God, when the powers of earth unite with the powers from beneath to oppress God's people, and when laws are made to compel worship according to human opinions. Under trial, those who apostatize may betray fellow believers to protect themselves, exposing that they lacked a vital union with Christ. The warning means cruel betrayal by friends and relatives should not surprise believers, and family opposition is no reason to refuse the gospel or turn from the truth. Those who face it must put on the whole armor of God to withstand in the evil day, with the promise that he who endures to the end will be saved.