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 Muhammad] - they are actually pledging allegiance to Allah. The hand of Allah 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 Allah - He will give him a great reward.
Context in Surah Al-Fath
Nearby ayahs help place verse 48:10 in sequence and meaning.
إِنَّآ أَرْسَلْنَـٰكَ شَـٰهِدًا وَمُبَشِّرًا وَنَذِيرًا
Indeed, We have sent you as a witness and a bringer of good tidings and a warner
لِّتُؤْمِنُوا۟ بِٱللَّهِ وَرَسُولِهِۦ وَتُعَزِّرُوهُ وَتُوَقِّرُوهُ وَتُسَبِّحُوهُ بُكْرَةً وَأَصِيلًا
That you [people] may believe in Allah and His Messenger and honor him and respect the Prophet and exalt Allah morning and afternoon.
سَيَقُولُ لَكَ ٱلْمُخَلَّفُونَ مِنَ ٱلْأَعْرَابِ شَغَلَتْنَآ أَمْوَٰلُنَا وَأَهْلُونَا فَٱسْتَغْفِرْ لَنَا ۚ يَقُولُونَ بِأَلْسِنَتِهِم مَّا لَيْسَ فِى قُلُوبِهِمْ ۚ قُلْ فَمَن يَمْلِكُ لَكُم مِّنَ ٱللَّهِ شَيْـًٔا إِنْ أَرَادَ بِكُمْ ضَرًّا أَوْ أَرَادَ بِكُمْ نَفْعًۢا ۚ بَلْ كَانَ ٱللَّهُ بِمَا تَعْمَلُونَ خَبِيرًۢا
Those who remained behind of the bedouins will say to you, "Our properties and our families occupied us, so ask forgiveness for us." They say with their tongues what is not within their hearts. Say, "Then who could prevent Allah at all if He intended for you harm or intended for you benefit? Rather, ever is Allah, with what you do, Acquainted.
بَلْ ظَنَنتُمْ أَن لَّن يَنقَلِبَ ٱلرَّسُولُ وَٱلْمُؤْمِنُونَ إِلَىٰٓ أَهْلِيهِمْ أَبَدًا وَزُيِّنَ ذَٰلِكَ فِى قُلُوبِكُمْ وَظَنَنتُمْ ظَنَّ ٱلسَّوْءِ وَكُنتُمْ قَوْمًۢا بُورًا
But you thought that the Messenger and the believers would never return to their families, ever, and that was made pleasing in your hearts. And you assumed an assumption of evil and became a people ruined."