From "Fundamentals of Economics......"

Thus, we can see that borrowing means to promise future production to someone else and that interest is additional future production promised. To be clear: When you borrow, you are not producing but there is the apparency of production since you gain the fruits of production without actually producing. You now must maintain your normal production level for survival plus additional production to pay back what was borrowed plus additional production to pay back the interest. So borrowing with interest is the promise of future production. In some backward places one can even borrow against the future production of one's own children and grandchildren.