To understand Christ's words about freedom, slavery, and debt, we have to understand the meaning of these ideas in his era in contrast with our own.
In Christ’s era, a large percentage of the population was in slavery, and slavery took many forms. Some slaves were private property while others were public property (i.e. the helots of the Spartans). There were also debt slaves, especially in the Christ’s region. These were people who were bound to others primarily because of their debts to them. Someone was obligated to remain in another person’s service because the slave owner the master money and couldn’t be free until they repaid it.
Debt slavery was simply the way in which people honored their financial obligations in an era in which there were many fewer options in terms of how people could keep track of debts and find employment. We don’t consider the fact that we have to work so that we can pay our debts as evil. We have more freedom because we have institutions to track those debts (banks), court systems to sue for debts, and many choices about how and where we work. Slavery in general was not considered an evil in Christ’s era. It was simply a way of life. Debt slavery was a way of dealing with debts that extended this existing system.
People did not hire regular on-going employees in the same way that people do today. Free people worked for other free people for wages to do a specific job: build a house or harvest a field (the parable of the vineyard owner hiring laborers). These were not permanent positions. The only usual permanent employment was some form of slavery. The word translated as “servant” in the Gospels is, with very few exceptions, the word for slave.
Freedom was clearly valuable but it was a challenge. With that freedom came the obligation of supporting yourself in a world where most jobs working for others were usually temporary. A free person in Christ’s era was more like a small business owner today. You have to have your own farm or flock or trade, like housebuilding or fishing, to support yourself. If not, you lived a very insecure existence drifting from job to job, going where the work was like today’s migrant workers.
There was a whole vocabulary related to “freedom” and “slavery” in Christ’s era that we cannot imagine in our own. It included ideas such as being a slave yourself, but having free children.
So, there is a very strong connection between freedom, slavery, and debt in Christ’s words. When Christ talks about debts, he is also talking about freedom. A debtor was either a slave or someone who would become a slave if he fell behind in his payments. The phrase translated in the Lord’s Prayer as “Forgiving trespasses” actually means “letting go of debts.” The phrase, “forgive those who trespass against us” means “let go of debtors.” This is another way of talking about giving someone their freedom.
Debt is connected to God because we all owe God everything. Every breath we take, we own to God. However, God also gives us free will. By doing, he forgives us our debts and sets us free. So, in Christ’s terms, we do not “owe” God obedience. If we did, we wouldn’t be free. We must give to God as freely as he gives to us.