John 15: 14 – 15
There were different kinds and levels of friendship in antiquity, and Greco-Roman writers often commented on the topic. Friendship could involve political or military alliances and was often pursued in self-interest; kings or lesser patrons who supported dependents called clients were (especially in Roman circles) said to be engaging in “friendship”; Pharisees also met in circles of “friends.” The traditional Greek concept of friendship emphasized equality among companions, and some philosophical schools like the Epicureans especially emphasized such friendship.
The main ideals of friendship in ancient literature included loyalty (sometimes to the death), equality and mutual sharing of all possessions, and an intimacy in which a friend could share everything in confidence. Jesus especially emphasizes the last point in verse 15, where he distinguishes a friend from a servant, who might also be loyal but would not share intimate secrets. Jewish writers like Philo sometimes contrasted being friends of God with being servants of God.
Keener, C. S. (1993). The IVP Bible background commentary: New Testament (Jn 15:14–15). Downers Grove, IL: InterVarsity Press.