What should the Muslim do whenever he hears a Hadeeth and doubts its authenticity? Taking into consideration that he may hear it in public transportation and he may not meet the person who said it again. May Allaah Grant you success to all that Pleases Him.

All perfect praise be to Allaah, The Lord of the Worlds. I testify that there is none worthy of worship except Allaah, and that Muhammad, sallallaahu ‘alayhi wa sallam, is His Slave and Messenger.

Conveying something that has been said by the Prophet, sallallaahu ‘alayhi wa sallam, is unlike conveying that of anyone else, for it was narrated on the authority of Al-Mugheerah that the Prophet, sallallaahu ‘alayhi wa sallam, said: “Ascribing lies to me is not like ascribing lies to anyone else. Whoever deliberately tells a lie about me, then let him take his seat in Hell.” [Al-Bukhari]

Thus, it is obligatory upon every Muslim to check the authenticity of any Hadeeth before attributing it to the Messenger of Allaah, sallallaahu ‘alayhi wa sallam.

Moreover, whoever hears anything of that kind and is sure that the Messenger of Allaah, sallallaahu ‘alayhi wa sallam, did not say it, should inform the one who is saying it that it cannot be attributed to the Messenger of Allaah, sallallaahu ‘alayhi wa sallam. In fact, this is included in the meaning of being sincere to Allaah The Almighty, His Messenger and all Muslims as it was narrated in the Hadeeth in which the Messenger of Allaah, sallallaahu ‘alayhi wa sallam, said:  “Religion is An-Naseeha.” We said (i.e. the Companions ), “To whom?” Then, he, sallallaahu ‘alayhi wa sallam, said, “To Allaah and His Book, and His Messenger, and to the leaders of the Muslims and their common folk.”  [Muslim]

Imaam An-Nawawi said in explaining the meaning of sincerity to the Messenger of Allaah, sallallaahu ‘alayhi wa sallam, that it is to revive his guidance and Sunnah, and to spread his Da‘wah and teachings, efface any falsity attributed to it and refrain from speaking about it without knowledge.

Allaah Knows best.