Some of Jesus’s teachings are hidden from those who have rejected him as the messiah. The Pharisees, for example, think they are wise and have understanding, but they do not (v. 25a). In the immediate context, the villages of Galilee thought themselves wise when they rejected the representatives of the messiah, so now the plan of redemption is hidden from them.
This anticipates the parables of the kingdom in Matthew 13. For the first time Jesus begins to teach the crowds using parables so that the insiders (the disciples, the little children) will understand, but the outsiders will not. What are the “hidden things” now revealed to the little children? In Matthew 13:11, Jesus says the “secrets (mysteries) of the kingdom of heaven” have been given to the disciples. Jesus taught his own disciples things which he did not teach the crowds.
The reason for this is that God chose to reveal his plan to “little children” (v. 25b). As in the previous unit, the little children are Jesus’s disciples. The noun translated “little children” in the ESV (νήπιος) refers to an infant, up to the age of a person who was not yet of legal age, so a minor (BDAG). But the LXX uses the word to translate the Hebrew word “simple,” and in secular Greek it is used figuratively for “infantile, childish, silly, ignorant, without foresight” (BrillDAG). To “speak like a child” is to say foolish things.
The emphasis is not on innocent children or babies, but the opposite of the wise and intelligent. In the context of Matthew, the ones who have rejected Jesus as the Messiah (Pharisees and teachers of the Law) are the intelligent and well educated. Jesus’s disciples have received God’s revelation through Jesus, yet they are (in comparison) like foolish children.
The difference between the wise (who do not understand) and the little children (who do understand) is that God has revealed the hidden things to the little children. This is the gracious will of God, which the Father handed over to Jesus (vv. 26-27). Father reveals to the Son, the Son reveals to the little children, the disciples.
Many have rejected Jesus as the messiah, but some have responded in faith. Those faithful are the “little ones” the children to whom the father has revealed the hidden things. But this does not mean the gospel is only for the insiders or that the wise who have rejected Jesus cannot yet come to Jesus. He therefore invites everyone to come to him and find rest.
I have occasionally heard this passage used as an excuse for not pursuing a biblical education or for pastors to avoid ministerial training. Some people have a perverse pride over being uneducated. But that is not the point here. Jesus is not making a statement about his uneducated disciples. In fact, the Parable of the Sower in Matthew 13 indicates they are well prepared to receive the word of God. Jesus has revealed himself publicly as the messiah, so that both his disciples and the Pharisees saw and heard the same things. The difference between the disciples and the Pharisees in Matthew is the Pharisees were not prepared to accept Jesus as the Messiah and reject him and eventually turn antagonistic towards him (in chapter 12).