One should not fast during the Days of Tashriq
MUSLIM 1141a:
from Nubayshah al-Hudhalī —
The days of Tashriq are the days of eating and drinking.
مسلم ١١٤١a:
عن نبيسهه الهذلي —
قَالَ رَسُولُ اللَّهِ ﷺ أَيَّامُ التَّشْرِيقِ أَيَّامُ أَكْلٍ وَشُرْبٍ