The Greek word translated “mystery” here, means “something that could not be known by men except by divine revelation, but that, though once hidden, has now been revealed in Christ and is to be proclaimed so that all who have ears may hear it.”
God’s truths are hidden for His children, not from them. God has given an open invitation to everyone to receive the spiritual rebirth which entitles them to the revelation of these mysteries of the Kingdom. But as stated in 1 Corinthians 2:14, a natural man cannot receive the things of the Spirit of God because they are spiritually discerned. Therefore, whoever rejects Jesus rejects the source of all wisdom and knowledge (Col. 2:3), thereby reserving the deep things of God for those who receive Jesus and draw on His wisdom through the Holy Spirit. This also safeguards the laws of God, upon which all the universe is founded, from being appropriated and misused by Satan’s kingdom.
In context, Jesus is speaking about those who have revelation knowledge of the mysteries of God. They will receive even more revelation and will walk in the abundant life that Jesus provided (Jn. 10:10; 2 Pet. 1:3). Those who do not receive God’s revelation will lose whatever truth they do have and will go farther and farther into deception. God reveals His truths to us in stages and not all at once (Isa. 28:9-10). Therefore, as we walk in the revelation of what the Lord has already shown us, He will reveal more of His truths to us.
The truths of God are mysterious only to those who do not soften their heart by seeking God with their whole heart. As Jeremiah 29:13 says, “And ye shall seek me, and find me, when ye shall search for me with all your heart.”