"Again, the Kingdom of Heaven is like a treasure hidden in the field, which a man found, and hid; and for joy, over it, he goes and sells all that he has, and buys that field." Matthew 13: 44
Treasures are hard to find; we must work hard to locate them! Thereafter, dig deep to filter tonnes of rumbles of rock to get a small amount of precious metals.
Precious metals are akin to treasure; Gold, Diamond, iron, rubies, emerald and all other precious metals are buried deep in the earth. God wants us to mine treasures through His word. When we gain it, we have access to the knowledge of His riches.