There is a link between BELIEF and OBEDIENCE that cannot be broken.
Hebrews 3 NKJV
18 And to whom did He swear that they would not enter His rest, but to those who did not obey? 19 So we see that they could not enter in because of unbelief.
Hebrews 3 AMPLIFIED
18 And to whom did He swear [an oath] that they would not enter His rest, but to those who disobeyed [those who would not listen to His word]? 19 So we see that they were not able to enter [into His rest—the promised land] because of unbelief and an unwillingness to trust in God.
From the Garden of Eden - a commandment was given but Eve trusted the words of a false prophet (serpent) over the word of God. Adam took of it and ate. He made a conscious choice to go against the commandment given (unbelief) and the rest is history.