Umar bin Yonus bin al-Qasim عمر بن يونس بن القاسم · The Book of al-Bay'ah

"We came in a delegation to the Messenger of Allah and my companions entered and asked their questions. I was the last of them to enter, and he said: 'What is you question?' I said: 'O Messenger of Allah, when will emigration end?' The Messenger of Allah said: 'Emigration will not cease so long as the disbelievers are being fought."'