3. Pureness of heart is inseparable from simplicity and humility. It excludes all ideas of selfishness and pride. This was why Jesus took infancy as the symbol of purity and humility.
It might appear unjust to make this comparison seeing that the Spirit of a child could be very old, and on being reborn to corporeal life might bring with it the imperfections which it had not been able to cast off during previous incarnations. Only a Spirit who has reached perfection can offer an example of true purity. However, from the point of view of our present life it offers an exact comparison because a child, having had no opportunity as yet to manifest any perverse tendencies, presents us with an image of innocence and purity. So it becomes clear that Jesus did not say the Kingdom of Heaven was meant for children, but for those who resemble them.