the Prophet granted the camel herders a concession allowing them to stone the Jamrat on one day an not another.  

أَنَّ النَّبِيَّ ﷺ رَخَّصَ لِلرُّعَاةِ أَنْ يَرْمُوا يَوْمًا وَيَدَعُوا يَوْمًا  

the Messenger of Allah granted a concession to some camel herders, allowing them to not stay overnight in Mina, and allowing them to stone the Jimar on the Day of Sacrifice, then to combine the stoning of two days after sacrifice, so that they could do it on one of the two days.  

أَنَّ رَسُولَ اللَّهِ ﷺ رَخَّصَ لِلرُّعَاةِ فِي الْبَيْتُوتَةِ يَرْمُونَ يَوْمَ النَّحْرِ وَالْيَوْمَيْنِ اللَّذَيْنِ بَعْدَهُ يَجْمَعُونَهُمَا فِي أَحَدِهِمَا