65:7 If one person lends money to a friend for a certain amount of time so that the friend will reciprocate and will later lend him a larger amount for the same length of time or the same amount for a longer period, this is also interest. If the intention is that the friend will lend him the same amount for the same length of time, the authorities differ as to whether or not it is interest; it is therefore advisable to act stringently in this matter and avoid the situation. However, if no condition was made and the one who initially borrowed later lends to him of his own accord, even if he is only doing so because he had previously borrowed, one may act leniently.
65:8 So long as the debt is outstanding, the lender must be careful not to benefit from the borrower without the borrower's knowledge. This even applies to something that the borrower would have done for the lender anyway, even if he had not lent him money. The reason for this is that since the lender enjoys something that is not his, it seems that he is relying on the unpaid loan to assume that the borrower would permit this. On the other hand, if the borrower knowingly does the lender a favor, it is permitted so long as it's something he would have done for him anyway, even without the loan. Nevertheless, such favors may not be made public knowledge.