Matthew 5: 43 - 48
43 "You have heard that it was said, `You shall love your neighbor and hate your enemy.'
44 But I say to you, Love your enemies and pray for those who persecute you,
45 so that you may be sons of your Father who is in heaven; for he makes his sun rise on the evil and on the good, and sends rain on the just and on the unjust.
46 For if you love those who love you, what reward have you? Do not even the tax collectors do the same?
47 And if you salute only your brethren, what more are you doing than others? Do not even the Gentiles do the same?
48 You, therefore, must be perfect, as your heavenly Father is perfect.

EWTN