According to the Hindu mythology, Goddess Lakshmi known as the goddess of wealth, fortune, and prosperity and is the wife of Vishnu. With Parvati and Saraswati, she forms Tridevi, the holy trinity. Moreover, Lakshmi Puja should be done at the Dhanteras throughout the Pradosh Kaal, which is known as the good muhurat for Lakshmi Puja which is started after the sunset and the end of next 1 hour and 43 minutes. Dhanteras Puja is also knwon as the Dhanwantari Triodasi.
Furthermore, Dhanteras is also the day for celebrating wealth, as the word 'Dhan' generally means wealth and 'Tera' comes from the date 13th of the Krishna paksha (the dark fortnight). However, it is believed that worshipping Goddess Laxmi and bringing new things on Dhanteras or Dhantrayodashi is a sign of good luck.
Story Behind Dhanteras
Lord Dhanvantari, who is considered to be the physician of Deities and an incarnation of Lord Vishnu, came out of the ocean that was churned by the Deities and the demons on the day of Dhanteras while, God Dhanvantari appeared with Ayurvedic for the well-being of the mankind.
Long ago, there was a king Hima. It was predicted about the son of King Hima that he would die on the 4th day of his marriage because of the snakebite death. At that time, when his intelligent wife came to know about such a prediction, she decided not to let her husband die and she made a plan. On the 4th day of their marriage she collected all the wealth and jewelleries at the entrance of the gate and lighted lamps, diyas at every nook and corner of the place and she then began to sing songs and started telling stories one after another in order to not let her husband sleep.
When it was the time for sleep, she lighten of the lights and diyaas, candles around the chamber and in the same time Lord Yama (the God of death) has arrived in guise of a snake.
Though, the bright lights and radiance of the lamps blinded his eyes and he could not enter their chamber. And due to the blindness, he kept sitting there for the whole night waiting to get a chance to bite the king's son. Alternatively, the wife kept singing songs and telling stories for the whole night thus he could not get any chance and in the morning Lord Yama left the place quietly.
In that regards, the wife saved her husband's life from the cruel commands of death and since then Dhanteras day is also known as the day of 'Yamadeepdaan' and it has become a ritual to light a lamps, diya and to keep it burning throughout the night in respect of Lord Yama, the God of death.