Surat Al Anfal: (43-44)

{إِذْ يُرِيكَهُمُ اللّهُ فِي مَنَامِكَ قَلِيلاً وَلَوْ أَرَاكَهُمْ كَثِيراً لَّفَشِلْتُمْ وَلَتَنَازَعْتُمْ فِي الأَمْرِ وَلَـكِنَّ اللّهَ سَلَّمَ إِنَّهُ عَلِيمٌ بِذَاتِ الصُّدُورِ} [الأنفال: 43]

43- O Prophet, remember when Allah showed you polytheists in your sleep few in number to inform your Companions and make them firm and courageous. However, if He had shown them to you in their real number, Muslims would have showed cowardice and differed regarding engaging in war, but Allah prevented that. Indeed, He is All-Knowing with that in your hearts and what you conceal of courage and grief.

{وَإِذْ يُرِيكُمُوهُمْ إِذِ الْتَقَيْتُمْ فِي أَعْيُنِكُمْ قَلِيلاً وَيُقَلِّلُكُمْ فِي أَعْيُنِهِمْ لِيَقْضِيَ اللّهُ أَمْراً كَانَ مَفْعُولاً وَإِلَى اللّهِ تُرْجَعُ الأمُورُ} [الأنفال: 44]

44- O believers, recall the favors of Allah upon you when Allah showed you the number of polytheists few so as to be courageous and yearn to quick victory to the extent that some of you thought them 70 or 100. On the other hand, He showed you few in the eyes of the disbelievers to tempt them to attack you to the extent that Abu Jahl said: The Companions of Muhammad are few, which made them abandon preparation.

However, when you started to engage with them, he made you large in number in the eyes of the polytheists so as to show cowardice and leave war. That management was done by Allah to ignite war between the two parties, raise the status of Islam and Muslims, and to humiliate the disbelievers. All matters belong to Allah who directs them as He wills.