William Burkitt on Matthew 5:43

Another corrupt gloss which the Pharisees had put upon the law of God, our Saviour here takes notice of: the law said, Thou shalt love thy neighbor, Lev 19:18. This they interpreted to relate only to their own countrymen, the Jews; concluding, that they might hate all the uncircumcised nations, as enemies; but, saith our Saviour, I require you to love all men; for if enemies must not be shut out of your love, none must.

Love your enemies: here the inward affection is required.

Bless them that curse you; there outward civility, and affability is required.

Do good to them that hate you; here real acts of our bitters and most malicious enemies.

Pray for them that despitefully use you, and persecute you: these are the highest expressions of enmity that can be, calumny and cruelty; yet are we commanded to pray for those that touch us in these two tenderest points, our reputation and sincere affection towards our most malicious enemies; to be ready upon all occasions to do good unto them, and pray for them.