Narrated Ibn 'Abbas:
that regarding "Alif Lam Mim. The Romans have been defeated" (In the nearest land, and they, after their defeat, will be victorious. Within Bid' years...) (30 1 & 2)" The Messenger of Allah (ﷺ) said to Abu Bakr about the wager: "Why were you not more cautious Abu Bakr? For indeed Al-Bid' refers to what is from three to nine." (ES)
English reference (ES): Vol. 5, Book 44, Hadith 3191 (ES)
Arabic reference (ES): Book 47, Hadith 3495 (ES)