"And remember, if you were a slave when the Lord called you, you are now free in the Lord. And if you were free when the Lord called you, you are now a slave of Christ" (I Corinthians 7:22 NLT).
Does this mean that if you were a slave then you are the property of your owner and forced to obey them?
Forced? No. There have always been slaves who rebelled against their masters. "Required to obey" would be a better way to put it. "If you keep My commandments, you will abide in My love, just as I have kept My Father's commandments and abide in His love" (John 15:10).
"Do you not know that to whom you present yourselves slaves to obey, you are that one's slaves whom you obey, whether of sin leading to death, or of obedience leading to righteousness? But God be thanked that though you were slaves of sin, yet you obeyed from the heart that form of doctrine to which you were delivered. And having been set free from sin, you became slaves of righteousness. I speak in human terms because of the weakness of your flesh. For just as you presented your members as slaves of uncleanness, and of lawlessness leading to more lawlessness, so now present your members as slaves of righteousness for holiness. For when you were slaves of sin, you were free in regard to righteousness. What fruit did you have then in the things of which you are now ashamed? For the end of those things is death. But now having been set free from sin, and having become slaves of God, you have your fruit to holiness, and the end, everlasting life. For the wages of sin is death, but the gift of God is eternal life in Christ Jesus our Lord" (Romans 6:16-23).
But in a real sense, we all belong to God. "Behold, all souls are Mine; The soul of the father As well as the soul of the son is Mine; The soul who sins shall die" (Ezekiel 18:4). This is why those who choose to rebel and serve a different master (sin) are under a death sentence.