“Love your enemies and pray.” The word “love” is the verb agapaō (#25 ἀγαπάω; the more familiar noun is agape). In this context, to love one’s enemy does not mean to “feel good” about them, but rather to act toward them in a loving manner. To better understand what God is telling us when He says, “love your enemies,” see the commentary on John 21:15, “I am your friend.”
The words, “bless them that curse you, do good to them that hate you,” which appear in the KJV, NKJV, and YLT, and partially in Darby’s NT, were not in the original text of Matthew. They were added by scribes who took them from Luke 6:27-28. Early manuscript evidence from Alexandrian, pre-Caesarean, Western, Coptic, and Syriac texts, indicates that the words are not original in Matthew. Also, some early manuscripts do not have both phrases, which is still more evidence that these two phrases were not in the original text of Matthew (see B. Metzger, A Textual Commentary on the Greek New Testament).