Surah Al-Anfal 8:9

إِذْ تَسْتَغِيثُونَ رَبَّكُمْ فَٱسْتَجَابَ لَكُمْ أَنِّى مُمِدُّكُم بِأَلْفٍ مِّنَ ٱلْمَلَـٰٓئِكَةِ مُرْدِفِينَ

[Remember] when you were asking help of your Lord, and He answered you, "Indeed, I will reinforce you with a thousand from the angels, following one another."

Translation: Saheeh International

Tafsir

When you sought help from your Lord asking Him to help you by granting you victory over them and He answered you saying ‘I shall reinforce you I shall assist you with a thousand angels rank upon rank’ one rank following after the next God promised them this number at first but it then became three thousand and then …

Excerpt from Tafsir al-Jalalayn, commentary on 8:9, via Quran.com. The reader has the full commentary and 9 more tafsirs.