25 Luke's account reads "At that time Jesus, full of joy through the Holy Spirit, said, "I praise you..." (Luke 10:21)
Jesus says God has hidden 'these things' (spiritual wisdom, salvation) from the 'wise and learned' and revealed them to 'little children.' So who are the 'wise and learned' and who are the 'little children'?
The 'wise and learned' are those who are wise in their own eyes (Isaiah 5:21; 1 Corinthians 1:20, 8:2; Galatians 6:3).
The 'little children' are representative of those who will enter the kingdom (Matthew 18:4, 19:13-15). They are those who 'humble themselves' and take the 'lowly position.' These are his disciples and those who receive Him.
From Matthew 18:4, we know that "whoever humbles themself" or "takes the lowly position" like a child is greatest in the kingdom. He speaks of the value in being humble (God have mercy on me, a sinner) and contrasts it with pride in Luke 14:11 (taking the seat of honor, the best seat for yourself) and Luke 18:14 (God, thank you I'm not like these wicked people). Jesus taught blessed are the poor in spirit and the meek (Matthew 5:3, 5). He said that whoever wants to be first must be a servant and a slave (Matthew 20:26-27, 23:11; Luke 22:25-27). (His contrasts include the disciples arguing about who would be the greatest and take over after Jesus left and the Pharisees who were desiring the seat of honor at the banquet.) And of course Jesus demonstrated this by washing the feet of his disciples (John 13:14).
26 Why would God be pleased to hide Spiritual things from the wise and learned yet reveal them to the 'humble' and those who take the 'lowly position'?
27 "All things"- probably authority of all knowledge of 'these things' (v. 25) necessary for repentance and acceptance of Jesus/his disciples. Jesus chooses (v. 27).
See Matthew 13:11, Mark 4:11-12.
Jesus words that 'no one knows the Son except the Father' is hard for me. Looking at the context, perhaps Jesus is saying 'the wisdom of this world doesn't give man wisdom of the Father or the Son. All things, all wisdom was given to the Son from the Father; and nobody knows the Son or the Father whom the Son has not chosen to reveal them to.'
After verse 27, Luke adds the following: "Then he turned to his disciples and said privately, “Blessed are the eyes that see what you see. For I tell you that many prophets and kings wanted to see what you see but did not see it, and to hear what you hear but did not hear it.” (Luke 10:23-24)
Come to me, Jesus. I am the one who has the words of eternal life. You will receive rest for your souls. Rest is the idea of peace with God and contrasting with toil: "Through painful toil you will eat of it [the ground] all the days of your life." (Genesis 3:17).
Also physical rest in this life. The people were weary and burdened by the heavy loads the Pharisees and teachers of the law were placing on the people (Matthew 23:4). They ask the people to obey them and do everything they tell them to do (Matthew 23:3). But they don't need to do these things; heck, the Pharisees don't even do them (Matthew 23:3)! It's useless, burdensome work that God doesn't require. Jesus requires no such things. Jeremiah 6:16: Jesus knows the good way to walk in. This will provide rest.
"It has been said by biblical scholars that the Pharisees had added over 600 regulations regarding what qualified as ‘working’ on the Sabbath. That is a heavy burden!" (Got Questions)
"...the contrast is between the burden of submission to the OT in terms of Pharisaic regulation and the relief of coming under Jesus' tutelage as under the authority of gentle revealer to whom the OT, the ancient paths, truly pointed." (Carson, 278-279)
D.A. Carson, The Expositor's Bible Commentary: Matthew, Volume 8 (Grand Rapids: Zondervan, 1984).
Got Questions: http://www.gotquestions.org/yoke-easy-burden-light.html.