There is a connection between acts of kindness to others and the blessing of God on their souls, just as there is a connection between the cruelties that we inflict on others and God’s recompense towards us. However, the unbeliever does not see this.
The merciful man is a picture of a believer in Christ who now has a different purpose for living and is concerned about souls and the mission of the church in the world, not his own enrichment, not his own pleasure. What matters to him is the great work and mission of Christ in winning souls from hell to heaven. The believer is concerned more about sanctification and personal change and he is interested in things that will help him in that regard. It is another reason for being an outgiving, unselfish, outflowing person spiritually.
Suppose that, even as a Christian, I am a person always interested in what I am going to buy next and what I can have and how much more I can have of it and so on. And I lapse into being a covetous Christian, out for gain, always watching the way things are treating me and what I am getting and so on. Don't you see, this will trouble me as a person before the Lord because it will make me increasingly self-seeking. Are we outgoing people, investing our energy in the work of the Lord, or are all our interests for ourselves? If we invest only in ourselves, it affects even us.