Sahih Muslim 2600 a
The Book of Virtue, Enjoining Good Manners, and Joining of the Ties of Kinship
Whomever Is Cursed, Reviled Or Prayed Against By The Prophet (ﷺ) When He Does Not Deserve That, It Will Be Purification, Reward And Mercy For Him
A'isha reported that two persons visited Allah's Messenger (ﷺ) and both of them talked about a thing, of which I am not aware, but that annoyed him and he invoked curse upon both of them and hurled malediction, and when they went out I said: Allah's Messenger (ﷺ) , the good would reach everyone but it would not reach these two. He said: Why so? I said: Because you have invoked curse and hurled malediction upon both of them. He said: Don't you know that I have made condition with my Lord saying thus: O Allah, I am a human being and that for a Muslim upon whom I invoke curse or hurl malediction make it a source of purity and reward.