Hadith: The worst lie is when a man claims to have seen something which he has not seen

عن ابن عمر رضي الله عنهما قال: قال النبي صلى الله عليه وسلم : «أَفْرَى الفِرَى أن يُرِيَ الرجل عينيه ما لم تَرَيَا».
[صحيح] - [رواه البخاري]

Ibn ‘Umar (may Allah be pleased with him) reported that the Prophet (may Allah's peace and blessings be upon him) said: "The worst lie is when a man claims to have seen something which he has not seen.”
[Authentic hadith] - [Narrated by Bukhari]

Explanation

The Prophet (may Allah's peace and blessings be upon him) explained that one of the worst types of lies is for a person to claim to have seen something, while awake or in his dreams, and he has not actually seen it. Lying about seeing something in a dream is worse than lying about seeing something in wakefulness, because what a person sees while being asleep is from Allah, the Almighty, via the angel if it is a vision. Therefore, lying in this case is considered lying about Allah. As for dreams, they are from the devil, and self-talk comes from the self. So, what the sleeping person sees is one of these three types.