Matthew 5:43

Ye have heard that it hath been said, Thou shalt love thy neighbor, and hate thine enemy - The command to love our neighbor was a law of God, Leviticus 19:18. That we must therefore hate our enemy was an inference drawn from it by the Jews. They supposed that if we loved the one, we must of course hate the other. They were total strangers to that great, special law of religion which requires us to love both. A neighbor is literally one that lives near to us; then, one who is near to us by acts of kindness and friendship. This is its meaning here. See also Luke 10:36.