Qitzur Shulchan Arukh – 65:9
If the borrower was not accustomed to greet the lender first at other time, he is prohibited from [making sure to] be first [now]. And he is prohibited from giving him any special honor in the synagogue or any other place, if he wouldn’t normally do so at other times. Similarly, all matters of “interest through speech” are forbidden, , as it is says (Devarim 23:20): “interest of anything that is lent on interest” [which can also be read “interest of any speech that is lent on interest”] — even [an increase that is only] speech is forbidden.
Similarly, the lender [too] is warned against interest through speech, eg: if he said to the borrower, “tell me if so-and-so comes from a certain place”. Even though he is only giving him the bother of making a statement alone, if he didn’t usually do this with him before this, and now he’s relying on the loan to [give him the authority to] order him, becauswe he is indebted to him, this is prohibited interest.
If one says, “But it is written (Mishle 22:7): “the borrower is a servant to the lender’!” This is only about matters where a dispute and issues arise between them, and the lender says “let’s go to the court to adjudicate there” and the borrower says “[no, let us] judge here”, the borrower is obliged to where the lender wants, the borrower is obliged to where the lender wants, and the lender is not obliged to go to a court in another place, because it says, “the borrower is a servant to the lender”.