I recently read online the claim that, "What truly matters is obedience."
And I do not in any way want to diminish the need for obedience.
But let me suggest that the Pharisees thought the same way, that, "What truly matters is obedience". They were so ultra-concerned with obedience that they tithed on even the smallest spices - mint, dill, and cumin.
But Jesus said there were weightier matters than this type of obedience - justice, mercy, fidelity.
Jesus spoke often to this issue. He said that if you're in the middle of a worship ritual - obedient sacrifice - and remember that you've got something against your neighbor, you were to leave your sacrifice at the altar and go deal with the neighbor issue.
He spoke about how food going into your mouth does not defile a person, no matter how "obedient" you might be concerning dietary restrictions; what matters is what is in, and what comes forth from, the heart.
He spoke about white-washing the outside obediently, but having a dead inner-man.
He spoke about praising God outwardly, with the lips, while the heart simply isn't in it.
Obedience is not about finding and enforcing every little legal nuance in a legal system; it's about having the spirit that drives you to want to please God. When you tell your ten-year old son to clean his room, and he obediently goes off to do it, you're pleased with his obedience. But when he gets distracted and pulls out a bunch of toys and makes the room worse, he's not at all being disobedient; he's being a ten-year old boy. He needs correction, not removal from the family.
Failure to precisely obey every jot and tittle does not equate to disobedience. What matters with your child is not his perfect performance; what matters is his attitude, his heart. Is he earnestly trying to do the right thing, even if he doesn't understand, or gets distracted, and fails to accomplish the exact goal you set for him?
In the old covenant, it was about a legal system written down on paper (rock, actually), in specific regulations such as "don't touch, taste, handle", that had to be taught one to another. But the new covenant is not like the old; it's written on the heart, and doesn't consist of regulations like "don't eat this; observe this holy day, etc", that has to be taught one to another. It's a matter of attitude - love - first for the Creator, and then for one another. It's a matter of where your heart is.
Now granted, if the heart is in the right place, one will seek to be obedient in all things. But a perfect score in Performance is not what God is looking at in the new covenant; Jesus got that score for us, which is given to us on the basis of our attitude and trust in him. He's looking at our hearts.
Willful disobedience absolutely will disqualify one from the reward. But an imperfect score will not disqualify us, because Jesus' perfect score is given to us (he even got baptized to fulfill even that detail of right-ness, not because *he* needed to be baptized, but because *we* need to be).
What matters is the heart.