Not wishing to reinvent the wheel, I refer you to the anonymous answer that cited the Old Testament scriptures on the Year of Jubilee in ancient Israel.
None of that has anything to do with modern nations and their "National debts". It has to do with respect for the principle of God's sabbath - with the Jubilee, the land was given an entire sabbath-year of rest. People were restored and returned to their dignified, land-owning state if they had lost that due to getting so much into debt that they'd had to enter bonded servitude to the one they owed money to. It kept the nation of ancient Israel on a sound, level basis. For as long as they glorified God in the nation, the land would give its produce. Also, they would stand out as singularly blessed by God, in contrast with the pagan nations around them. The sabbath principle was one of the outstanding identifying marks of God's covenant people.
Due to the ancient nation of Israel breaking its covenant and sabbath requirements to God, God punished the nation eventually. They were taken into Babylonian captivity for 70 years, with Jerusalem wrecked and the temple destroyed, to let the land recover and 'catch up' on all the neglected sabbaths it should have had.
Christians are told in the New Testament to "Owe no man anything, except love." Romans 13:8-10. Until Christians get back to that principle, we will suffer the virtual slavery of being in financial debt, and nations will have crippling national debt - all because of love of money (which is idolatry). No nation on Earth is in a covenant relationship with God now. It is individual Christians, in every nation, who are. Let Christians be free of debt and forgiving, and respect the principle of sabbath-rest.