St. Peter of Damaskos (12th Century) writes:
“Men are three kinds: slaves, hirelings or sons.
Slaves do not love the good, but refrain from evil out of fear of punishment; this, as St. Dorotheos observes, is a good thing, but not fully in accord with God’s will. Hirelings love what is good and hate what is evil, out of hope of reward.
But sons, being perfect, refrain from evil, not out of fear of punishment, but because they hate evil violently; and they do what is good, not because they hope for the reward, but because they consider it their duty. They love dispassion because it imitates God and leads Him to dwell in them; through it they refrain from all evil, even if no punishment threatens them.” (The Philokalia: Volume 3, pg. 168)
St. Paul the Apostle writes:
“Have this mind among yourselves, which is yours in Christ Jesus, who, though he was in the form of God, did not count equality with God a thing to be grasped, but emptied himself, taking the form of a servant, being born in the likeness of men.
And being found in human form he humbled himself and became obedient unto death, even death on a cross.
Therefore God has highly exalted him and bestowed on him the name which is above every name, that at the name of Jesus every knee should bow, in heaven and on earth and under the earth, and every tongue confess that Jesus Christ is Lord, to the glory of God the Father.” (Philippians 2:5-11)