Is there a sin in lying and concealing the donor's identity to avoid showing off (riya') when donating to a patient with kidney failure?

"You have done well in your eagerness to help this girl and your caution against showing off (riya') and consuming unlawful earnings, and we ask Allah to reward you with good. If you instructed the man who delivered the money to tell her something contrary to the truth, then you have done wrong, for this is a lie that no necessity calls for. You could have simply informed her that the money was from a good-doer. Repentance is obligatory upon both of you, and you must be careful that the fear of showing off does not become a barrier to doing good."