The world is rightly repulsed by the idea of slavery. But Scripture does not likewise shy away from the topic. Instead, it consistently employs the vivid imagery of slaves and masters to illuminate the believer’s relationship to Christ.
And the glorious truth is that, in Christ, we do not have a malicious, domineering, abusive Master. On the contrary, we see borne out in the pages of Scripture that tremendous liberty and blessing flow out of our submissive obedience to Him.
Not Mere Slaves, But Slaves Who Are Friends
Perhaps the key passage on Jesus’ demand for implicit obedience is John 15:14-15.
You are My friends if you do what I command you. No longer do I call you slaves, for the slave does not know what his master is doing; but I have called you friends, for all things that I have heard from My Father I have made known to you.
Notice, first of all, the fundamental principle this passage begins with: obedience. He is the Lord who commands them, and they are expected to obey. He was their Master, and they were His subordinates, duty-bound to do whatever He said. His authority over them was absolute, and their obedience was to be unequivocal—or else they were no friends of His.
It is vital to understand that Jesus was not suggesting that obedience makes someone His friend—as if His favor could be earned through service. He was saying, however, that obedience is a singular proof that someone is His friend. Implicit obedience to His commandments is the necessary, expected, and natural fruit of genuine love for Him. It is also therefore the telltale mark of authentic saving faith. Again, a necessary inference is that someone who does not do what Jesus says is not a friend of His at all. He was describing as clearly as possible a master-slave relationship.
But the why does He say, “No longer do I call you slaves . . . I have called you friends”? Is He expressly telling them their relationship with Him was now a familiar personal camaraderie between colleagues, rather than a master-slave relationship governed by authority and submission? Does that part of the statement show that He was disclaiming the whole slave metaphor?
Not at all. Look at the context. First, He expressly indicates that He had called them slaves—because that is precisely what they were: douloi, with Him as their uncontested kurios (Master). That relationship, by definition, cannot change. So in verse 15 He is simply saying they were His friends as well as His slaves. And He clearly explains why He makes a differentiation between mere slaves and friends: “The slave does not know what his master is doing.” In other words, a slave’s obedience is implicit, unhesitating; and he is not owed any explanation or rationale from the Master. He is to obey whether he understands why or not.
But Jesus had kept nothing secret from His disciples. His purposes were fully known to them: “All things that I have heard from My Father I have made known to you” (John 15:15). They were therefore much more than mere slaves to Him. They were His friends as well, privy to His thoughts and purposes (cf. 1 Corinthians 2:16). In a similar way, every ruler would have friends among his subjects to whom he might reveal personal matters, but they were still his subjects. Friendship with one’s lord or master does not nullify the authority inherent in the relationship.
This concept of friendship between master and slave was not unknown in Roman times (cf. Philemon 15-17), but it was highly unusual. The tension between slaves and slave owners was—as we might expect—usually filled with enmity. Murray Harris cites a Latin proverb which said anyone who owns many slaves also has many enemies. Jesus turned that principle on its head by bringing His disciples into the circle of intimate friendship. He makes His slaves His friends by His love for them.
The love is mutual, of course, but the status is not. He was still their Lord and they were still His douloi. In other words, as friends, they were not his “buddies” in the sense of being casual chums or peers with Him in the relationship. He remained their Lord and Master, and they belonged completely to Him.
Slavery and True Liberty
So understood correctly, the gospel is an invitation to slavery. When we call people to faith in Christ, we need to stress that fact in the same way Jesus did. On the one hand, the gospel is a proclamation of freedom to sin’s captives and liberty to people who are broken by the bondage of sin’s power over them. On the other hand, it is a summons to a whole different kind of slavery: “Having been freed from sin, you became slaves of righteousness” (Romans 6:18). As the apostle Peter wrote, “Act as free men, and do not use your freedom as a covering for evil, but use it as bondslaves of God” (1 Peter 2:16).
Both sides of the equation are vital. There is a glorious freedom in being the slaves of Christ, because “if the Son makes you free, you will be free indeed” (John 8:36). On the other hand, being a true follower of Christ means the end of human autonomy. And that is as it should be, because self-determination turns out to be nothing more than an illusion anyway. The only kind of liberty it offers is “free[dom] in regard to righteousness” (Romans 6:20)—and that is the very essence of bondage to sin. Its inevitable end is death and destruction. If we want true liberty from sin and all its fruits, it is not autonomy that we need, but a different kind of bondage: complete surrender to the lordship of Christ.
In other words, everyone serves some master. No one is truly independent and self-governing. We are all enslaved in one way or the other. In the words of the apostle Paul:
Do you not know that when you present yourselves to someone as slaves for obedience, you are slaves of the one whom you obey, either of sin resulting in death, or of obedience resulting in righteousness? But thanks be to God that though you were slaves of sin, you became obedient from the heart to that form of teaching to which you were committed, and having been freed from sin, you became slaves of righteousness. I am speaking in human terms because of the weakness of your flesh. For just as you presented your members as slaves to impurity and to lawlessness, resulting in further lawlessness, so now present your members as slaves to righteousness, resulting in sanctification. For when you were slaves of sin, you were free in regard to righteousness. (Romans 6:16-20)
No message can rightly be called the gospel if it glosses over or denies those truths. The gospel according to Jesus calls sinners to give up their independence, deny themselves, submit to an alien will, and abandon all rights in order to be owned and controlled by the Lord. By confessing Jesus as Lord (Kurios) we automatically confess that we are His slaves (douloi).
What does this mean in practical terms? To borrow the words of Edwin Yamauchi,
It means that we have been captured, beaten, and enslaved. We discover, however, that our captor is a Despot of love and mercy. Neither is there anything slavish or servile about our slavehood, for we have not received the spirit of bondage again to fear but the spirit of adoption (Romans 8:15). Nor has our reduction to slavery been a debasement or an abasement. . . . We have been elevated to serve in a heavenly court and have been invested with a higher nature.
. . . [It also] reminds us of our ransom from another master at an incredible price. It was not with the fabulous sums of all the royal estates we were bought, nor was it for handsome features or some prized skill we were purchased. But rather unlovely, without any merit, rebellious at heart, we were redeemed with the precious blood of the Master Himself.
Having thus been bought by Christ we are entirely His.  Edwin Yamauchi, “Slaves of God,” Journal of the Evangelical Theological Society 9, no. 1 (Winter 1966), 48-49.
There is no other possible way to view it.
There is also no legitimate way to adjust that message to make it sound appealing to people who admire Jesus but are not prepared to serve Him.
Jesus Himself never catered to that perspective. He was not seeking admirers; He was calling followers—not casual followers, but slaves. That explains why He demanded His disciples’ implicit obedience, and when He encountered people who were unwilling to obey unconditionally, He discouraged them from following Him at all.
Thus He declared his lordship without hesitation or apology, and He made it clear that true faith in Him begins with an unconditional surrender of the sinner’s heart. And therefore the very spirit of saving faith is comparable to the demeanor of a slave. It is a glorious surrender, and it is the supreme joy of every true believer’s heart to be Christ’s slave. But remove that spirit of submission, and the most profound kind of “admiration” for Christ is not even true faith at all. Yielding completely to Christ’s lordship is that vital an element of true saving faith, and therefore the proclamation of His lordship is an absolutely necessary component of the true gospel.
It is the unifying idea in the story of redemption, the song of the redeemed, and the reason for the gospel in the first place, “that at the name of Jesus every knee will bow, of those who are in heaven and on earth and under the earth, and that every tongue will confess that Jesus Christ is Lord, to the glory of God the Father” (Philippians 2:10-11).
(Adapted from The Gospel According to Jesus.)