Jesus expanded on one other area of the law in this chapter.  He dealt with the “second commandment,” thou shalt love thy neighbor as thyself (Matt 22:35-40).  The Old Testament reference for this command is found in Lev 19:18.  However, Jesus added “and hate thine enemy,” which was not a part of the original command.

The enemies that they hated were their national enemies and the enemies of God.  They hated the Moabites, for instance, in Deut 23:6.  In Mal 1:1-3 we see that God hated Esau.  Thus, David said that he counted the enemies of God his enemies and hated them with perfect hatred, Ps 139:21-22.

Jesus said that now they were to love their enemies.  This was not a command for them to become passive doormats for every evil abuse, but rather a command to view their enemies with compassion since Jesus was about to die for them so that he could save their souls.  They were to love their enemies for the sake of the gospel.  After all, the original soul winners who brought the gospel to the Gentiles were all Jews (Acts 15:7; Acts 9:15).  And the Gentiles had aforetime been their enemies (Eph 2:12-22).

Concerning v.44, we, as Christians are supposed to do the same thing that Jesus commanded his Jewish disciples to do:

Love your enemies – Rom 12:20
Bless them that curse you
Do good to them that hate you – Rom 12:14
Pray for them which despitefully use you
And persecute you – Acts 7:60

Why are we to do these things?  We are to do these because the Christian life is filled with reproach; the enemies of God don’t want Jesus Christ, initially, and we must suffer their cursing, hatred and persecution to get them the gospel (1 Pet 4:13-16).

Concerning v.45, Jews were already children of their Father from Ex 4:22.  However, by doing good to their enemies, their special relationship as God’s children would be known.  We became God’s children by adoption into the family of God through the new birth (Jn 1:12; Gal 4:3-7).  Thus our motive for doing good to our enemies is Eph 4:32.  In either case, God does good to his enemies by giving them sunshine and rain, without which they could not live.

Jesus said, in v.46-47, it was not enough to just love and salute those that love and salute you.  Anybody can do that.  In order to be like “your Father” (perfect, like a perfect fit, not sinless, Job 1:1) you’d have to love your enemies.  You see, Jesus loved us when we were enemies (Rom 5:8) and left us an example of how we should love others who don’t love us (1 Pet 2:19-24).