"But solid food is for the mature, who by constant use have trained themselves to distinguish good from evil." NIV
"But strong meat belongeth to them that are of full age, even those who by reason of use have their senses exercised to discern both good and evil." KJV
The natural order of growth for human development is to steadily gain in height and weight while at the same time learning different things. It takes food that is appropriate for age and advancement of the child. The same hold true for the born again children of God. Many Christians accept the Lord Jesus as their Saviour but they fail to get into the Word of God and make it a part of their everyday lives and they fail to faithfully commune with Him on a daily basis. They are not able to spiritually chew and digest the deep things of God, only the milk and elementary things of God. The answer is to take responsibility for working out our salvation, for hiding the Word in our heart, and growing up in Him.
Heavenly Father, we stand in need of Your grace and mercy as we work out our salvation in the way You intended. Help us to receiveYour Word and by it grow into mature Christians. Show us the way and give us the desire to grow and surrender so that we will be ready for spiritual meat, the deep things of Your kingdom. In Jesus' name we pray, Amen.