Hisham said, "My father said that 'Aishah (ra) used to observe Saum (fast) on the days of Mina." His (i.e., Hisham's) father also used to observe Saum on those days.  

أَخْبَرَنِي أَبِي كَانَتْ عَائِشَةُ ؓ تَصُومُ أَيَّامَ مِنًى وَكَانَ أَبُوهَا يَصُومُهَا  

Nobody was allowed to fast on the days of Tashriq except those who could not afford the Hadi (Sacrifice).  

أَنْ يُصَمْنَ إِلاَّ لِمَنْ لَمْ يَجِدِ الْهَدْىَ  

Fasting for those who perform ,Hajj-at-Tamattuʿ (in lieu of the Hadi which they cannot afford) may be performed up to the day of ʿArafat. And if one does not get a Hadi and has not fasted (before the ʿId) then one should fast of the days of Mina. (11, 12 and 13th of Dhul Hajja).  

الصِّيَامُ لِمَنْ تَمَتَّعَ بِالْعُمْرَةِ إِلَى الْحَجِّ إِلَى يَوْمِ عَرَفَةَ فَإِنْ لَمْ يَجِدْ هَدْيًا وَلَمْ يَصُمْ صَامَ أَيَّامَ مِنًى وَعَنِ ابْنِ شِهَابٍ عَنْ عُرْوَةَ عَنْ عَائِشَةَ مِثْلَهُ