David’s response to Saul’s death in 2 Samuel 1 highlights the principal of loving his neighbour, even to the extent of mourning and avenging Saul’s death. He recognised that Saul was God’s anointed, even though Saul chose to disobey God.
In Matthew 18 also we find advice about the way we interact with others. Jesus highlights the importance of the meek, teachable spirit of children, the necessity to remove temptation, and to care for that which is lost, whether it is a sheep or our brother. If we’re aware of someone’s sin, then it is our responsibility to assist them rather than publicly reprimanding them. Jesus also shows the importance of forgiving one another an unlimited amount, just as God continually forgives us.