There are three orders and estates of Christians, according to St. Basil the Great. Some are slaves, who out of fear of punishment do not do what is evil; others are hirelings, who do what is good for the sake of the reward and enjoyment of the Kingdom of Heaven; and others are as sons, who joyfully do what is good for its own sake and solely out of love for their Master.
We see now that these three estates are obliged to keep all of the Lord’s commandments. For if a particular Christian is in the rank of slaves and fears lest he be chastised and punished, he is compelled to carry out all of his master’s injunctions and not to neglect even the least of his commandments, if he wishes to escape punishment. If he is in the rank of hirelings, he is likewise bound to fulfill all that he is commanded by him who has hired him for his vineyard, because if he fails to do so, he cannot receive all of his wages. If he is in the rank of sons, it is his duty to show himself obedient and well-pleasing to his father in all things, and not to cause him even the slightest distress.
“It is not possible for those who fear to omit anything that they have been enjoined to do or to perform it carelessly. But even the hireling will not want to transgress anything that he is ordered to do; for how will he earn wages for his work in the vineyard if he does not fulfill all that has been agreed upon?… What son, whose goal it is to please his father, will wish to gladden him in more important matters while grieving him over the most insignificant ones?” (St. Basil, long Rules: Preface, 3)
And if God ordered the people of the old Israel to keep all of His commandments, how much more does He now order Christians, who are His chosen people, a beloved people that has been redeemed by His precious blood, to keep His commandments. (On Christian Morality, Discourse XIII)