Jeremiah 22

“Shall you reign because you enclose yourself in cedar?
Did not your father eat and drink,
And do justice and righteousness?
Then it was well with him.
16 He judged the cause of the poor and needy;
Then it was well.
Was not this knowing Me?” says the Lord. vv.15-16

Read chapter 22
What does it mean to know God?  
King Josiah was a king of Judah who was upright and did what was right in God's eyes, yet his sons after him did not rule as he did.  Josiah lived like a king and his heart was right before God, yet his sons (son, grandson, great grandson) who followed after him lived like kings yet with an evil heart towards God's commands and His people.  Josiah restored the temple during his day, getting rid of all idol worship and high places.  His sons built their own places in vain.  Josiah defending the curse of the poor and needy, his sons used defraud and unjust means from the poor to build themselves palaces.  They knew the way of duty having watched and known their father Josiah that led to his peace with God and the people, but they refused to walk in his steps.  To truly know God is to obey His will and to obey His will is to know what it is and to know what it is one must read His word and not just listen but be doers of the word.
Do you know God?  "Grace and peace be multiplied to you in the knowledge of God and of Jesus our Lord," 2 Peter 1:2