Matthew 5: who is the Lord? who is the Father?

In the Old Testament we read a lot about "the day of the Lord", a day where justice is made, a day of punishment. In chapter 4, we read:

17 From that time Jesus began to preach and say, “Repent, for the kingdom of heaven has come near.”

Why to repent? To escape the punishment in the day of the Lord according to many prophets. The Lord is merciful but it is necessary to repent before the day of the Lord as it is necessary to repent before our death because one day we all will have to face the Lord.
In Matthew 5 we read the Sermon on the Mountain. In special we read:

43-47 “You’re familiar with the old written law, ‘Love your friend,’ and its unwritten companion, ‘Hate your enemy.’ I’m challenging that. I’m telling you to love your enemies. Let them bring out the best in you, not the worst. When someone gives you a hard time, respond with the supple moves of prayer, for then you are working out of your true selves, your God-created selves. This is what God does. He gives his best—the sun to warm and the rain to nourish—to everyone, regardless: the good and bad, the nice and nasty. If all you do is love the lovable, do you expect a bonus? Anybody can do that. If you simply say hello to those who greet you, do you expect a medal? Any run-of-the-mill sinner does that.
48 “In a word, what I’m saying is, Grow up. You’re kingdom subjects. Now live like it. Live out your God-created identity. Live generously and graciously toward others, the way God lives toward you.”


It is very common for us, Christians, to think of ourselves as the chosen people as the Jews thought about themselves. Nothing wrong about it, but what is wrong is to listen to

“Repent, for the kingdom of heaven has come near.”

and say: my neighbor needs repentance, not me. But in the sermon of the mountain, it becomes clear that the chosen people are the ones who should repent. In particular because, there are many aspects of our lives who don't fit to the will of the Lord as we read in MSG:

"You’re kingdom subjects. Now live like it. Live out your God-created identity."

Certainly I am sure that I should love more my enemies. I should greet the one who doesn't greet me because the Father loves my enemy too.
In summary, the Lord that punishes is the same Father who loves his enemies and expect repentance.