A couple of things strike me in this passage.
First, the kinds of people who joined David. They were desperate, in debt, and discontented. In short, they were as Jesus put it, “poor in spirit.”
They were far from perfect men, but they became part of David’s kingdom.
It’s the same with us. Many us come to Jesus in weakness. We are hurting and struggling, and the things of this world just don’t satisfy us.
We also see how broken we are because of our sin.
But Jesus receives us, and says to us,
Blessed are the poor in spirit,
for the kingdom of heaven is theirs. (Matthew 5:3)
The second thing is that through David’s sin (his lie to the priest at Nob), many perished. He took responsibility for his own sin, and gave the priest Abiathar shelter.
We, on the other hand, caused the death of David’s descendant Jesus through our sin. And yet, he took responsibility for our sin, taking upon himself the punishment we deserved on the cross. So now when we come to him, humble and broken, he says to us, “Stay with me. Don’t be afraid…You will be safe with me.”
And he gives us peace.