Zao Jun has been worshipped as a god in China since at least the 2nd century BCE. There are several stories as to how he became a god, the most popular being that he was once a mortal man named Zhang Lang (張__) and was married to a virtuous woman. However Zhang Lang fell in love with a young girl and left his wife for her. From that day on he was plagued with bad luck to punish him for his betrayal. He was struck blind, the young girl left him and he had to resort to begging.
One day, while begging for alms, he happened across the house of his former wife, being blind he did not recognise her, and despite his shoddy treatment of her she took mercy on him and invited him in. She cooked him a meal and tended to him lovingly, he related to her his story and as he began to cry his eyesight was miraculously restored recognising his benefactress as his former wife he was overcome with shame and threw himself into the kitchen hearth not realising that it was lit!
His wife tried to save him but he was consumed by the fire and all that was left of him was a leg (to this day in China a fire poker is sometimes called Zhang Lang's Leg). His wife lovingly created a shrine to him above the fireplace where he died, this began Zao Jun's association with the stove in Chinese homes.
Alternatively Zao Jun was a man so poor he was forced to sell his wife. Years later he unwittingly became a servant in the house of her new husband. Taking pity on him she baked him some cakes into which see had hidden money, but he failed to notice this and sold the cakes for a pitence. When he realised what he had done he took his own life in despair. In both stories Heaven takes pity on Zhang Lang's tragic story and instead of becoming a vampirish Gui, the usual fate of suicides he was made the god of the Kitchen and was reunited with his wife.
Traditionally every Chinese household would have a paper effigy of Zao Jun and his wife (who writes down everything that is said in the household over the year for her husbands report to Yu Huang) above the fireplace in the kitchen and this tradition is still widely practiced. Offerings of food and incense are made to Zao Jun on his birthday which is said to be the third day of the eighth lunar month and also on the twenty third day of the twelfth lunar month when he returns to Heaven to give his New Year's report, on this day also the lips of Zao Jun's paper effigy may be smeared with honey to sweeten his words to Yu Huang (or keep his lips stuck together). After this the effigy will be burnt to be replaced by a new one on New Year's day and firecrackers are lit to speed him on his way to heaven. If the household has a statue of Zao Jun it will be taken down and cleaned on this day for the new year.The Story of Zao Jun
Worship and Customs