Did Jesus lay down his life for his friends or for his enemies?

Both, because they are the same people seen at different times. Paul describes what they were when Christ died: “while we were yet sinners, Christ died for us” (Romans 5:8), and “when we were enemies, we were reconciled to God by the death of his Son” (5:10). Jesus, speaking to his disciples on the night before his death, describes what his death makes of them: “Ye are my friends, if ye do whatsoever I command you” (John 15:14), no longer servants but friends (15:15). His death turns enemies into friends.

John 15:13 does not say that Christ died only for friends. It states the highest love known among people, to die for one’s friends, and Paul says that God’s love goes further still: “scarcely for a righteous man will one die” (Romans 5:7), “But God commendeth his love toward us” in dying for sinners (5:8). The same Jesus prayed at the cross for those who were crucifying him, “Father, forgive them; for they know not what they do” (Luke 23:34; some early manuscripts, among them Codex Vaticanus and Codex Bezae, lack this prayer, though most have it). John Gill notes that the friends for whom Christ laid down his life were not friends to begin with: he died for them as enemies, and so made them friends.