Nuns in Lancaster have described as "sickening" the theft from their convent of a collection box containing Pakistan flood relief funds.
The jar of cash contained £100 from ticket sales for a prayer and pasta night that the nuns of the Ursuline Convent are holding on Friday evening.
Two boys and a man, who trespassed in the grounds, were shown out of the convent by a nun before the theft.
Lancashire Police said "stealing from elderly nuns is despicable".
The theft from the convent at St Thomas More Walk happened at about 1230 BST on Wednesday.
Sister Superior Zela Proctor said: "It's tragic that people in Pakistan, who have lost everything, should be deprived of a little contribution that could have helped bring some small degree of comfort.
"The people who did this don't seem to have any feeling. It makes you really sick."
Det Con Corinne Cleasby of Lancashire Police said: "Stealing from elderly nuns, especially when the money was destined to help those who are in dire need because of a natural disaster, is quite despicable.
"I hope that this appeal may prick someone's conscience and that they will come forward with information."
The man was described as white, in his 30s, of average build, with short blond or ginger hair and wearing a white t-shirt.
The two boys were aged between six and eight and were both wearing white t-shirts.