Question:
If somebody lends me money… Can I tell him “I appreciate” ?
Answer:
It is forbidden to pay any kind of interest on a loan, and this includes even something purely verbal, such as blessing the lender for lending you the money.
To say “Thank you,” however, is permitted by some (though not all) authorities, because they regard this not as a favour for the lender but rather as simply good manners.
Saying “I appreciate this” is perhaps similar because it is not so much a blessing to the lender as a statement intended to indicate that I am not so ungrateful as to not acknowledge the loan.
