Dāna: Giving
Giving is the first ground of merit. Barzillai hauled beds, wheat, honey, and cheese across the Jordan to a king who had nothing, at the hour when a gift costs the giver most: a man in flight cannot repay, and nobody yet knew which way the war would turn. Goods handed over at the moment of need weigh more than the same goods sent in a settled season.
Suhada: The true-hearted friend
One mark of a true-hearted friend is standing by you in misfortune. Absalom's revolt emptied Jerusalem, and the men who had eaten at David's table when there was a table were gone; an eighty-year-old landowner came out to Mahanaim instead. Fair-weather company shows up for the meal, and this kind of friend shows up for the flight.
Kataññutā: Knowing what was done for you
Gratitude begins as memory, holding onto a deed after the need it met has passed. Dying, working through his accounts with Joab and with Shimei, David has that supper come back to him whole, years on, with the giver's name still attached. Rescue fades quickly once a person is safe again, and keeping hold of it takes deliberate effort.
Puñña: Merit, the good a deed keeps making
Wholesome action goes on working long after the doer has finished it. Food carried into the wilderness for a hunted man becomes, a generation later, standing places at the royal table for sons who were never at Mahanaim. Barzillai asked nothing and went home to be buried by his parents' grave, and the good still arrived, by a road he never planned.
Mettā: Goodwill
Goodwill is simply wanting another to do well. "Show kindness" falls on the sons, who fed no one and risked nothing, and a seat at the king's table is a standing arrangement, bread for life rather than a single dinner. Warmth of this sort runs past the ledger, paying out to children what was owed to their father.