Cross reference
Mark 10:15
15 Truly I say to you, Whoever does not put himself under the kingdom of God like a little child, will not come into it at all.
Matthew 18:3
3 And said, Truly, I say to you, If you do not have a change of heart and become like little children, you will not go into the kingdom of heaven.
Luke 18:17
17 Truly I say to you, Whoever does not put himself under the kingdom of God like a little child, will not come into it at all.
John 3:3-6
3 Jesus said to him, Truly, I say to you, Without a new birth no man is able to see the kingdom of God.
4 Nicodemus said to him, How is it possible for a man to be given birth when he is old? Is he able to go into his mother's body a second time and come to birth again?
5 Jesus said in answer, Truly, I say to you, If a man's birth is not from water and from the Spirit, it is not possible for him to go into the kingdom of God.
6 That which has birth from the flesh is flesh, and that which has birth from the Spirit is spirit.