Matthew 18:3, “Truly, I say to you, unless you turn and become like children, you will never enter the kingdom of heaven.”
Here, as in other places, Christ condemns human reason as a means to entering God’s kingdom. Misinformed Christians like Baptists, Calvinists, and others believe a child must first understand before they are baptised and enter God’s kingdom. Yet that is not what Jesus describes here. All people, He says, must become like a child—like the children who were before Him that day. These children were being brought to Christ by their parents. The children, unable to understand who Jesus is, are unable to express their faith; thus, their responsible parents brought them to Jesus so that He might bring them into the kingdom. Preventing such entry is condemned by Jesus.
Therefore, the kingdom of God belongs to children, for saving faith does not rely on understanding; saving faith, rather, relies on the work of the Holy Spirit, whose mysterious ways we cannot perceive. Let us, therefore, bring our children before Christ without hesitation in order to be baptised into His kingdom. And let us adults also come to Christ like children who cannot fathom His ways, but nevertheless trust in who He is—the God of mercy and grace.
The Lutheran Column 