David needed men to pledge their allegiance to his kingdom. 
Without invitation bands of warriors began to show up at David’s front door to offer their services. They dedicated themselves to seeing him succeed. 
David, surrounded by these men, moved forward in gaining the kingdom. Because of their presence and talents he was encouraged to go on in God’s will for his life. 
What a picture of how the family of God should work! We don’t need to wait for a person to ask us for help. Instead we need to ask God who we could be a help to.