”What is the kingdom of Christ? A rule of love, of truth—a rule of service. The king is the chief servant in it. ‘The kings of the earth have dominion: it shall not be so among you.’ The great Workman is the great King, laboring for his own. So he that would be greatest among them, and come nearest to the King himself, must be the servant of all. It is like king, like subject in the kingdom of heaven.  No rule of force, as of one kind over another kind. It is the rule of kind, of nature, of deepest nature—of God. If, then, to enter into this kingdom, we must become children, the spirit of children must be its pervading spirit throughout, from lowly subject to lowliest king. The lesson added by St. Luke is: ‘For he that is least among you all, the same shall be great.’ And St. Matthew says: ‘Whosoever shall humble himself as this little child, the same is greatest in the kingdom of heaven.’ Hence the sign that passes between king and subject. The subject kneels in homage to the kings of the earth: the heavenly king takes his subject in his arms. This is the sign of the kingdom between them. This is the all-pervading relation of the kingdom.” 

________________________________________________________________________________

Commentary

"No rule of force, as of one kind over another kind. In this rule of kind, of nature, of deepest nature - of God...the spirit of children must be the pervading spirit throughout...This is the sign of the kingdom between them. This is the all-pervading relation of the kingdom." 
---George MacDonald