Ibn Abbas once was asked:
What are the best days, months, and the best deeds? The best days are the Fridays, the best months are the Ramadan month, and the best deeds are the on time five times daily prayers, he responded.
When the commander of the faithful, Imam Ali (AS) heard of this, said: if the scholars of the west and east were asked this question, they had no answer but this, but my answer differs and is this:
The best deed is the one which God accepts it, and he best month is the one in which you do penance, and the best day is the one in which you pass away while you are a believer.
source : erfan.ir