The mind that would push the small and defenseless away is the ego guarding its gates, deciding who is worthy of love and who must be kept out. But the awakened teacher within refuses that sorting, for the kingdom belongs to whatever comes without defense. To come as a child is to arrive without the armor of judgment, trusting rather than bargaining, open rather than guarded.
This openness is not weakness but the one condition in which love is recognized. The ego calls it foolish and would forbid it, because a mind that no longer defends itself has nothing left to fear and nothing left to attack. That undefended trust is the very door through which heaven is remembered.
Little children: the part of the mind that comes without defenses, the trusting and undefended state in which love is received rather than earned.