This fast is kept on the Ekadashi of Krishna Paksha of Kartik month. This Ekadashi is called Rambha or Rama Ekadashi. For married women, this fast is said to be auspicious and give happiness. On this day, worship Lord Krishna with all things; distribute prasad by doing naivedya and aarti. On the Dwadashi date, after feeding the Brahmin and giving Dakshina, send him away, then the fast should take food.
In ancient times, there was a righteous king named Muchukunda. He used to fast on every Ekadashi. The people of the state also started observing fast on every Ekadashi. The king had a daughter named Chandrabhaga. She also used to fast on Ekadashi.
She was married to Shobhan, the son of King Chandrasen. Shobhan lived with the king. That's why he also started fasting on Ekadashi. On the Ekadashi of Krishna Paksha of Kartik month, Shobhan fasted for Ekadashi but died due to hunger. Due to this the king, queen and daughter were very sad but kept on fasting on Ekadashi.
Shobhan got residence in Dev Nagar situated on the Mandarachal mountain due to the effect of fasting. There Rambhadi Apsaras were ready in his service. Suddenly one day Muchukunda went to the Mandarachal mountain and there he saw Shobhan. After coming home, he told all the story to the queen and daughter. The daughter went to her husband after getting this news and both started living happily. Rambhadi Apsaras were engaged in his service. That's why this Ekadashi is called Rambha Ekadashi.