Sunan At-Tirmidhi

Narrated Abu Sa'eed:""On the Day of (the battle of) Badr, the Romans had a victory over the Persians. So the believers were pleased with that, then the following was revealed: Alif Lam Mim. The Romans have been defeated..."" up to His saying: '...the believers will rejoice. (30:1-4)"" He said: ""So the believers were happy with the victory of the Romans over the Persians