Sayyiduna Abdullah bin Abbas (may Allah be pleased with them both) says: When the Messenger of Allah (peace and blessings be upon him) struck Quraysh on the day of Badr and returned to Madinah, he gathered the Jews in the market of Qaynuqa' and said: "O community of Jews! Accept Islam before there befalls you the like of what befell Quraysh." They said: "O Muhammad! Do not be deceived about yourself because you killed a group of Quraysh who were unacquainted with war. If you fight us, you will know that we are real fighters; you have not yet met people like us." So Allah Almighty revealed these verses concerning this saying of theirs: "Say to those who disbelieve: You will soon be overcome and gathered into Hell, and it is the worst resting place." [Surah Al Imran: 12] "There has already been a sign for you in the two groups that met: one group fighting in the way of Allah and the other disbelieving; those disbelievers saw the Muslims as twice their own number with their own eyes. Indeed in that is a lesson for those who have vision." [Surah Al Imran: 13]
Hadith Referenceالسنن الكبرى للبيهقي / كتاب السير / 18629