A brief look at the Hebrew shows us a difference in the original text used by different translations. If you have the cool software you can note two Hebrew words with the numbers 2617a and 1580. The first is “merciful” in both the KJV and NASB but while the second appears in both translations it is associated with different English words. It seems to be just a matter of the translators having issues because the meaning comes through the same for both.
The point is that our attitude and intent tend to be boomerangs. They eventually loop back and hit us in everyday life. I don’t think this is a short term promise. I think it is a long term principle. Jesus put it this way,
(Matthew 5:7 KJV) Blessed are the merciful: for they shall obtain mercy.I like to think about how He had to Old Testament scriptures in mind when He spoke.
So? If you want the best out of life, give the best.