He sent a hadeeth in order to spread good, then he found out that it is a fabricated hadeeth. What should he do?
Question

                I got a message in my e-mail which contained a hadeeth narrated from the Prophet (peace and blessings of Allaah be upon him). At the end of the letter, as is usual, it asked the recipient to send it to everyone he knows so as to spread the benefit of it. I sent it to many people, then I found out that the hadeeth is mawdoo’ (fabricated). Some good people told me that I should send a letter to everyone to whom I sent it, telling them that the hadeeth is fabricated. The problem is that I do not know who I sent this letter to. Is there any sin on me or do I have to pray for forgiveness? Please note that the hadeeth does not contain any legislation, rather it is a story that is supposed to have happened when the Messenger (peace and blessings of Allaah be upon him) was circumambulating the Ka’bah and there was a Bedouin circumambulating with him, etc.
Praise be to Allah.
    Spreading da’wah messages and letters which contain 
    explanations of shar’i rulings, or preaching and beneficial stories, is an 
    important means of doing good, because many people receive them, and it is 
    easy to send them. But we should make sure that the content is sound and 
    that the ahaadeeth contained in it are saheeh (sound), because some people 
    are abusing this great blessing (of easy communication) and are spreading 
    fabricated ahaadeeth and false stories. 

    It is not permissible for anyone to say, “The Messenger of 
    Allaah  (peace and blessings of Allaah be upon him) said…” when he knows 
    that the hadeeth is mawdoo’ (fabricated) or false. The Prophet  (peace 
    and blessings of Allaah be upon him) said: “Whoever tells lies about me 
    deliberately, let him take his place in Hell.” Narrated by al-Bukhaari, 
    1291; Muslim, 933. 

    And he  (peace and blessings of Allaah be upon him) said: 
    “Whoever narrated a hadeeth from me which he thinks is false, then he is one 
    of the liars.” Narrated by Muslim in the Introduction to his Saheeh. 

    Al-Nawawi (may Allaah have mercy on him) said in Sharh 
    Muslim (1/71): 

    It is haraam to narrate a fabricated hadeeth for one who 
    knows that it is fabricated or who thinks it most likely that it is 
    fabricated. Whoever narrates a hadeeth which he knows or thinks it most 
    likely to be fabricated, and does not explain that it is fabricated, is 
    included in this warning and is included among those who tell lies about the 
    Messenger of Allaah  (peace and blessings of Allaah be upon him). This 
    is also indicated by the hadeeth quoted above: “Whoever narrated a hadeeth 
    from me which he thinks is false, then he is one of the liars.” Hence the 
    scholars said that the one who wants to narrate or quote a hadeeth must 
    check it. If it is saheeh or hasan, then he may say, “The Messenger of 
    Allaah  (peace and blessings of Allaah be upon him) said such and such, 
    or did such and such, etc”, expressing certainty. If it is da’eef (weak), 
    then he should not say, “he said” or “he did” or “he commanded” or “he 
    forbade” and other such definitive words, rather he should say, “Such and 
    such was narrated from him” etc, or “it was narrated” or “it was said” or 
    “we heard that” and so on. And Allaah, may He be glorified, knows best. End 
    quote. 

    He also said: 

    With regard to the prohibition on telling lies about the 
    Prophet  (peace and blessings of Allaah be upon him), no distinction is 
    made between reports which contain rulings and those which do not contain 
    rulings, such as preaching and exhortation, etc. In all cases it is haraam 
    and is a major sin and abhorrent action, according to the consensus of the 
    Muslims whose consensus counts, unlike the innovators who falsely claim that 
    it is permissible for fabricate ahaadeeth of exhortation, and who are 
    followed in that by many of the ignorant who claim to be ascetics. End 
    quote. 

    With regard to what you have done by spreading this 
    fabricated hadeeth, the expiation for that is to ask Allaah for forgiveness 
    and to strive to inform everyone to whom you think you most likely sent this 
    hadeeth that the hadeeth is fabricated. And Allaah burdens not a person 
    beyond his scope [al-Baqarah 2:286]. 

    You should not spread any hadeeth after this until you make 
    sure that they are soundly attributed to the Messenger of Allaah  (peace 
    and blessings of Allaah be upon him). 

    And Allaah knows best.