The sculptures and the paintings of the lord Shiva are always seen wearing a crescent over his head. There is a story behind this tradition of Lord Shiva wearing a crescent, thereason behind this tradition is the curse given to the moon by his father-in-law Daksh. Let us tell you the full story here..
Daksha, the master of civilization, had married twenty seven of his daughters – the Nakshatras, lunar asterisms, to moon-god, Chandra. But Chandra ignored the 26 Nakshatrams and was enamored by only one among them the beautiful Rohini.
The other daughters complained to Daksha about Chandra’s partisan behavior and this angered Daskha who cursed Chandra that your body of which you are so proud will fade away.
Soon the body of Chandra started fading away and he approached Lord Vishnu who directed him to Lord Shiva who is the supreme physician and the keeper of the sacred herb Soma.
Chandra went to Prabhasa tirtha and made a linga on the banks of the river Sarasvati. He prayed to Shiva for six months.
At the end of the tapasya Shiva appeared before Chandra and offered to grant him a boon. Chandra explained what the problem was.
Lord Shiva helped Chandra in regaining his lost luster and glory with the herb Soma. But Daksha cursed him again and he took the help of Lord Shiva and this continued for a long period. Shiva said, “Daksha’s curse cannot be entirely ignored. Let us have a compromise. During krishnapaksha you will wane. And during shuklapaksha (the bright part of the lunar fortnight) you will wax. That should satisfy everybody.”
Finally, Shiva being the graceful Almighty, asked Chandra to take refuge in his lock of hair on his head where he will find enough soma to rejuvenate him periodically making him grow for 15 days and decay for 15 days periodically.
Thus the curse of Daksha causes the moon to wane and Lord Shiva rejuvenates him to wax again.