The ruling on one who doubts that his relative died because of the treatment he gave him

He has a second question as well, in which he says: I had a sister who passed away twenty-five years ago. She was ill, and her illness was severe. There were no doctors available to us, and there was nothing to benefit her except that people advised me to give her a drink to relieve the pain in her stomach. So I gave her the drink, and after a few days she passed away from the same illness. After many years, I began to have doubts that perhaps this drink affected her and she died because of it. Do I have a sin on me, and do I owe an expiation?
Answer: Leave these doubts alone; they are from Satan. As long as the drink was in her interest and was prescribed for you by someone with experience in such matters, then you did well in giving it. You owe nothing, and there is no blame on you; in fact, you are rewarded. Leave the doubts that Satan brings to people; there is no blame on you and no sin on you, and you have done well. There is no power and no strength except with Allah. Yes.