The one consistent requirement of God for His people, that we listen and obey, was true before the Law, under the Law, and under Grace3.
The requirement for Adam before the Law:
Genesis 2:15-17 NIV
The LORD God took the man and put him in the Garden of Eden to work it and take care of it.  And the LORD God commanded the man, "You are free to eat from any tree in the garden;  but you must not eat from the tree of the knowledge of good and evil, for when you eat from it you will certainly die."
Adam heard and knew both the requirement and the penalty from God but did not obey. And through Adam sin and death reigned in the world. Obedience was required under the Law as given by Moses at Gerizim to Israel (emphasis mine):
Deuteronomy 28:1-2 AMP
Now it shall be, if you diligently listen to and obey the voice of the LORD your God, being careful to do all of His commandments which I am commanding you today, the LORD your God will set you high above all the nations of the earth. All these blessings will come upon you and overtake you if you pay attention to the voice of the LORD your God.
If we obey the "voice of the LORD" the blessings will "overtake" us. In the Words of Jesus (emphasis mine):
Luke 11:28 NIV
He replied, "Blessed rather are those who hear the word of God and obey it."
Matthew 7:24-27 NIV
"Therefore everyone who hears these words of mine and puts them into practice is like a wise man who built his house on the rock.  The rain came down, the streams rose, and the winds blew and beat against that house; yet it did not fall, because it had its foundation on the rock.  But everyone who hears these words of mine and does not put them into practice is like a foolish man who built his house on sand.  The rain came down, the streams rose, and the winds blew and beat against that house, and it fell with a great crash."
When Jesus spoke in parables He often ended with "He who has ears, let him hear." The one consistent requirement of God, under any dispensation, is listening and obeying. If you don't listen how can you obey? In Matthew 6:6 Jesus said "when you pray..." We are expected to pray. Matthew 6:9-15 give the pattern for prayer I will explore more of this passage in the coming weeks.