She was Fatima, the mother of Dawud, a great grandson of the 2nd Imam, Hasan al- Mujtaba (A.S.) and a foster brother of the 6th Imam, Ja‘far al-Sadiq (A.S.). Umm Dawud had served as a wet nurse to Imam as-Sadiq (A.S.).
Once, the 6th Imam (A.S.) was ill so Fatima (Umm Dawud) went to visit him. During her visit the Imam inquired about his [foster] brother Dawud. Fatima replied that she had lost hope in finding him, for she did not even know whether he was alive or dead. The Imam taught her an A‘mal (a combination of Qur’anic recitations, supplications and prayers) that was very effective in getting a quick outcome of one’s legal needs. It is said that, whoever performs this A‘mal, the doors of skies are opened for him/her, and the angels descend from heavens to receive him and to inform him of the good news of acceptance.
Umm Dawud said that she waited till she performed the A‘mal on 15th of Rajab. The next day someone knocked the door and, to her amazement it was her son Dawud, who got released from the prison. Dawud narrated to her mother that he was held in a very high security prison with chains on his neck, hands and feet. Suddenly, one fine day the guards came in and took him to Mansur, the ruler. He ordered the chains to be removed, gave Dawud ten thousand Dirhams, and a fast ride to take to him home.
It is reported authentically that Umme Dawood asked whether this Amal can be performed in any other month than Rajab. The Holy Imam replied in the affirmative and said that it can be performed on Day of Arfa and if perchance Arfa falls on Friday, the performer will not have finished yet that he will be absolved of his sins.
This Amal can be performed in any month. One should observe fast on 13th, 14th and 15th day of the month and recite this Do'a on 15th as described above. His wish inshaallah will be fulfilled.