The Prophet (ﷺ) said: The greatest war, the conquest of Constantinople and the coming forth of the Dajjal (Antichrist) will take place within a period of seven months.
Sunan Abi Dawud Book 39, Hadith 5
← Previous Hadith The Prophet (ﷺ) said: The flourishing state of Jerusalem will be when Yathrib is in ruins, the ruined state of Yathrib will be when the great war comes, the outbreak of the great war will be at the conquest of Constantinople and the conquest of Constantinople when the Dajjal (Antichrist) comes forth. He (the Prophet) struck his thigh or his shoulder with his hand and said: This is as true as you are here or as you are sitting (meaning Mu'adh ibn Jabal).

Sunan Abi Dawud Book 39, Hadith 4 Next Hadith → The Prophet (ﷺ) said: The time between the great war and the conquest of the city (Constantinople) will be six years, and the Dajjal (Antichrist) will come forth in the seventh.

Abu Dawud said: This is sounder than the tradition narrated by Isa (bin Yunus)

Sunan Abi Dawud Book 39, Hadith 6