[Machine] That the Messenger of Allah ﷺ used to perform a voluntary prayer before the obligation of the fifth of the spoils of war. When the verse was revealed "And know that anything you obtain of war booty - then indeed, for Allah is one fifth of it" [Surah Al-Anfal 41], he left the voluntary prayer that he used to perform and it became one fifth of one fifth for Allah's share and one fifth for the Prophet's share ﷺ.  

أَنَّ رَسُولَ اللهِ ﷺ كَانَ يُنَفِّلُ قَبْلَ أَنْ تَنْزِلَ فَرِيضَةُ الْخُمُسِ فِي الْمَغْنَمِ فَلَمَّا نَزَلَتِ الْآيَةُ {أَنَّمَا غَنِمْتُمْ مِنْ شَيْءٍ فَأَنَّ لِلَّهِ خُمُسَهُ} [الأنفال 41] تَرَكَ النَّفْلَ الَّذِي كَانَ يُنَفِّلُ وَصَارَ ذَلِكَ إِلَى خُمُسِ الْخُمُسِ مِنْ سَهْمِ اللهِ وَسَهْمِ النَّبِيِّ ﷺ  

[Machine] He heard Sa'id ibn al-Musayyib saying, "People used to give the voluntary charity from the fifth."  

أَنَّهُ سَمِعَ سَعِيدَ بْنَ الْمُسَيِّبِ يَقُولُ كَانَ النَّاسُ يُعْطَوْنَ النَّفْلَ مِنَ الْخُمُسِ  

[Machine] I rode horses in the period of ignorance and I did not realize that people only perform voluntary acts of worship (such as giving a fifth of their income as charity).  

لَقَدْ رَكِبْتُ الْخَيْلَ فِي الْجَاهِلِيَّةِ وَمَا أَدْرَكْتُ النَّاسَ يُنَفِّلُونَ إِلَّا مِنَ الْخُمُسِ