The Prophet (ﷺ) said to Ibn Saiyad, "I have kept for you a secret." Ibn Saiyad said, "Ad-Dukh." The Prophet said, "Keep quiet, for you cannot go beyond your limits (or you cannot exceed what has been foreordained for you)." On that, `Umar said (to the Prophet (ﷺ) ), "Allow me to chop off his neck!" The Prophet said, "Leave him, for if he is he (i.e., Ad-Dajjal), then you will not be able to overcome him, and if he is not, then you gain no good by killing him."
Sahih al-Bukhari Book 82, Hadith 24
← Previous Hadith When taking an oath, the Prophet (ﷺ) very often used to say, "No, by Him Who turns the hearts."

Sahih al-Bukhari Book 82, Hadith 23 Next Hadith → I asked Allah's Messenger (ﷺ) about the plague. He said, "That was a means of torture which Allah used to send upon whom-so-ever He wished, but He made it a source of mercy for the believers, for anyone who is residing in a town in which this disease is present, and remains there and does not leave that town, but has patience and hopes for Allah's reward, and knows that nothing will befall him except what Allah has written for him, then he will get such reward as that of a martyr."

Sahih al-Bukhari Book 82, Hadith 25