كتاب المغازى
64  
Military Expeditions led by the Prophet (pbuh) (Al-Maghaazi)
(29)
Chapter: The Ghazwa of Al-Khandaq or Al-Ahzab Battle
(29)
باب غَزْوَةُ الْخَنْدَقِ وَهْىَ الأَحْزَابُ
Sahih al-Bukhari 4116

Narrated `Abdullah:

Whenever Allah's Messenger (ﷺ) returned from a Ghazwa, Hajj or `Umra, he used to start (saying), "Allahu- Akbar," thrice and then he would say, "None has the right to be worshipped except Allah alone Who has no partners. To Him belongs the Kingdom, all praises are for Him, and He is able to do all things (i.e. Omnipotent). We are returning with repentance (to Allah) worshipping, prostrating, and praising our Lord. Allah has fulfilled His Promise, made His Slave victorious, and He (Alone) defeated the clans (of infidels) ."

حَدَّثَنَا مُحَمَّدُ بْنُ مُقَاتِلٍ، أَخْبَرَنَا عَبْدُ اللَّهِ، أَخْبَرَنَا مُوسَى بْنُ عُقْبَةَ، عَنْ سَالِمٍ، وَنَافِعٍ، عَنْ عَبْدِ اللَّهِ ـ رضى الله عنه ـ أَنَّ رَسُولَ اللَّهِ صلى الله عليه وسلم كَانَ إِذَا قَفَلَ مِنَ الْغَزْوِ، أَوِ الْحَجِّ، أَوِ الْعُمْرَةِ، يَبْدَأُ فَيُكَبِّرُ ثَلاَثَ مِرَارٍ ثُمَّ يَقُولُ ‏ "‏ لاَ إِلَهَ إِلاَّ اللَّهُ وَحْدَهُ لاَ شَرِيكَ لَهُ، لَهُ الْمُلْكُ وَلَهُ الْحَمْدُ، وَهْوَ عَلَى كُلِّ شَىْءٍ قَدِيرٌ، آيِبُونَ تَائِبُونَ عَابِدُونُ سَاجِدُونَ، لِرَبِّنَا حَامِدُونَ، صَدَقَ اللَّهُ وَعْدَهُ، وَنَصَرَ عَبْدَهُ، وَهَزَمَ الأَحْزَابَ وَحْدَهُ ‏"‏‏.‏
Reference : Sahih al-Bukhari 4116
In-book reference : Book 64, Hadith 160
USC-MSA web (English) reference : Vol. 5, Book 59, Hadith 442
  (deprecated numbering scheme)