Narrated Ibn 'Abbas:

from 'Umar bin Al-Khattab, who said: "The Prophet ﷺ looked over the idolaters, and there were a thousand of them, while his Companions were three-hundred and ten and some odd number of men. So the Prophet of Allah ﷺ faced the Qiblah, stretched forth his hands and began beseeching his Lord: 'O Allah! Fulfill what You promised for me. [O Allah! Bring about what You promised for me] O Allah! If you destroy this band of adherents to Islam, you will not be worshiped upon the earth,' He continued beseeching his Lord with his hands stretched, facing the Qiblah until his Rida fell from his shoulders. Abu Bakr came to him, took his Rida and placed it back upon his shoulders, then embraced him from behind and said: 'O Prophet of Allah! You have sufficiently beseeched your Lord, indeed He shall fulfill what He promised you.' So Allah, Blessed and Most High, revealed: When you sought help of your Lord and He answered you (saying): 'I will help you with a thousand of the angels in succession (8:9).'

حَدَّثَنَا مُحَمَّدُ بْنُ بَشَّارٍ، حَدَّثَنَا عُمَرُ بْنُ يُونُسَ الْيَمَامِيُّ، حَدَّثَنَا عِكْرِمَةُ بْنُ عَمَّارٍ، حَدَّثَنَا أَبُو زُمَيْلٍ، حَدَّثَنَا عَبْدُ اللَّهِ بْنُ عَبَّاسٍ، حَدَّثَنَا عُمَرُ بْنُ الْخَطَّابِ، قَالَ نَظَرَ نَبِيُّ اللَّهِ ﷺ إِلَى الْمُشْرِكِينَ وَهُمْ أَلْفٌ وَأَصْحَابُهُ ثَلاَثُمِائَةٍ وَبِضْعَةَ عَشَرَ رَجُلاً فَاسْتَقْبَلَ نَبِيُّ اللَّهِ ﷺ الْقِبْلَةَ ثُمَّ مَدَّ يَدَيْهِ وَجَعَلَ يَهْتِفُ بِرَبِّهِ " اللَّهُمَّ أَنْجِزْ لِي مَا وَعَدْتَنِي اللَّهُمَّ آتِنِي مَا وَعَدْتَنِي اللَّهُمَّ إِنْ تُهْلِكْ هَذِهِ الْعِصَابَةَ مِنْ أَهْلِ الإِسْلاَمِ لاَ تُعْبَدُ فِي الأَرْضِ " . فَمَا زَالَ يَهْتِفُ بِرَبِّهِ مَادًّا يَدَيْهِ مُسْتَقْبِلَ الْقِبْلَةِ حَتَّى سَقَطَ رِدَاؤُهُ مِنْ مَنْكِبَيْهِ فَأَتَاهُ أَبُو بَكْرٍ فَأَخَذَ رِدَاءَهُ فَأَلْقَاهُ عَلَى مَنْكِبَيْهِ ثُمَّ الْتَزَمَهُ مِنْ وَرَائِهِ فَقَالَ يَا نَبِيَّ اللَّهِ كَفَاكَ مُنَاشَدَتُكَ رَبَّكَ فَإِنَّهُ سَيُنْجِزُ لَكَ مَا وَعَدَكَ فَأَنْزَلَ اللَّهُ : (إِذْ تَسْتَغِيثُونَ رَبَّكُمْ فَاسْتَجَابَ لَكُمْ أَنِّي مُمِدُّكُمْ بِأَلْفٍ مِنَ الْمَلاَئِكَةِ مُرْدِفِينَ ) فَأَمَدَّهُمُ اللَّهُ بِالْمَلاَئِكَةِ . قَالَ هَذَا حَدِيثٌ حَسَنٌ صَحِيحٌ غَرِيبٌ لاَ نَعْرِفُهُ مِنْ حَدِيثِ عُمَرَ إِلاَّ مِنْ حَدِيثِ عِكْرِمَةَ بْنِ عَمَّارٍ عَنْ أَبِي زُمَيْلٍ وَأَبُو زُمَيْلٍ اسْمُهُ سِمَاكٌ الْحَنَفِيُّ وَإِنَّمَا كَانَ هَذَا يَوْمَ بَدْرٍ .