the Messenger of Allah went to a camel, and took a hair from its hump between his fingers and said: "I am not entitled to take anything from the Fay, not even this, except the Khumus, and the Khumus will come back to you."
أَنَّ رَسُولَ اللَّهِ ﷺ أَتَى بَعِيرًا فَأَخَذَ مِنْ سَنَامِهِ وَبَرَةً بَيْنَ إِصْبَعَيْهِ ثُمَّ قَالَ إِنَّهُ لَيْسَ لِي مِنَ الْفَىْءِ شَىْءٌ وَلاَ هَذِهِ إِلاَّ الْخُمُسُ وَالْخُمُسُ مَرْدُودٌ فِيكُمْ
the Messenger of Allah went to a camel, and took a hair from its hump between his fingers and said: "I am not entitled to take anything from the Fay, not even this, except the Khumus, and the Khumus will come back to you." (Using translation from Nasāʾī 4139)
أَنَّ رَسُولَ اللهِ ﷺ أَتَى بَعِيرًا فَأَخَذَ مِنْ سَنَامِهِ وَبَرَةً بَيْنَ إِصْبُعَيْهِ ثُمَّ قَالَ «هَا إِنَّهُ لَيْسَ لِي مِنَ الْفَيْءِ شَيْءٌ وَلَا هَذِهِ إِلَّا الْخُمُسُ وَالْخُمُسُ مَرْدُودٌ فِيكُمْ»