Almighty Allah in Surat al-Nazi'aat 79:30 speaking clearly about Dahwul Ardh says: “and the earth-after that He spread it out (dahahaa)...”
1. What is Dahwul Ardh?
“Dahwul Ardh” - the 25th of Dhulqa'dah, according to a tradition of the Holy Prophet (s) reported by one of his Sahabi - 'Abdullah bin Mas'ud, is the day when the earth was spread for the advantage of human beings. The phrase "Dahwul Ardh" literally means “The spread of the earth”. In another tradition it is reported that the first Rahmah & blessing descended on this very day.
A saying of a Masoom (as) goes: “Imam-e-Zamana Ajja lallahu Farajahu will rise in this day and will fill the world with fairness and justice as it was filled with unfairness and oppression”.
Hence it is a very important occasion indeed. This day is one of those four days, which are distinguished for the excellence of fasting. According to a tradition of the Holy Prophet (saw), whosoever fasts on this day his fast would equal 70 years of fasting. Many aamaal of this day have been described.
Having known these merits, should we limit our celebration with fasting and the expression of joy, or should our struggle transcend beyond that? This obviously would depend on our vision about this important day. And in order to understand properly the importance of this day, we should understand the earth better.
2. How is Dahwu'l Ardh applicable in the present era & how must we celebrate it?
Islam was not revealed for a certain time and a particular people. Its laws and teachings apply for all ages to come. We should try to appreciate this vital truth and behold the "universality" of the religious teachings.
The day of Dahwul Ardh that the Holy Prophet (saw) and our aimma (A) mention in the traditions was not a day of celebration for their time only. Rather it is a day to be celebrated in every epoch and land. The problems the earth faced in their time may be different from the problems the earth confronts in our age. However both have lived in the same earth.
Our duty in every age when this Islamic earth day is celebrated should be to ponder over this God-given blessing, the reason why it was created, whether it is utilized for the purpose it was created, the crisis it faces at present, the remedy for such crisis, etc. This would really make the celebration a celebration of true faith and concern, and a celebration of thanking the All-Merciful Creator who created the world for man's good.
source : www.hujjat.org