Surah Al-Fath 48:10

إِنَّ ٱلَّذِينَ يُبَايِعُونَكَ إِنَّمَا يُبَايِعُونَ ٱللَّهَ يَدُ ٱللَّهِ فَوْقَ أَيْدِيهِمْ ۚ فَمَن نَّكَثَ فَإِنَّمَا يَنكُثُ عَلَىٰ نَفْسِهِۦ ۖ وَمَنْ أَوْفَىٰ بِمَا عَـٰهَدَ عَلَيْهُ ٱللَّهَ فَسَيُؤْتِيهِ أَجْرًا عَظِيمًا

Indeed, those who pledge allegiance to you, [O Muḥammad] - they are actually pledging allegiance to Allāh. The hand of Allāh is over their hands. So he who breaks his word only breaks it to the detriment of himself. And he who fulfills that which he has promised Allāh - He will give him a great reward.

Translation: Saheeh International

Tafsir

Truly those who pledge allegiance to you the ‘Pledge of Beatitude’ bay‘at al-ridwān given at al-Hudaybiyya in fact pledge allegiance to God — this statement is akin to Whoever obeys the Messenger verily obeys God Q. 480. …

Excerpt from Tafsir al-Jalalayn, commentary on 48:10, via Quran.com. The reader has the full commentary and 9 more tafsirs.