Sunan Abi Dawud 4294
سنن أبي داود#4294HasanNarrated Mu'adh ibn Jabal: 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)
Scholarly Authentication
We show the most cautious grade (weakest-wins) as the overall label. Individual scholars graded it as follows:
Al-AlbaniHasan
Muhammad Muhyi Al-Din Abdul HamidHasan
Zubair Ali ZaiHasan
In-book reference: 39:4