Hadith

Amir al-Muminin, Imam Ali (pbuh)

 إنَّمَا هُوَ عِيدٌ لِمَنْ قَبِلَ اَللَّهُ صِيَامَهُ وَ شَكَرَ قِيَامَهُ وَ كُلُّ يَوْمٍ لاَ يُعْصَى اَللَّهُ فِيهِ فَهُوَ عِيدٌ

It is an Eid for him whose fasting Allah accepts and of whose prayers He is appreciative; and (in fact) every day wherein no sin of Allah is committed is an Eid

 Nahjul Balaghah, words of wisdom, No. 428