The hand-written petition dated September 12, 2012, which has been made public more than a month after Qasab was hanged, shows glaring Urdu language errors.
The application has been provided to Lucknow-based activist Urvashi Sharma under the Right to Information Act.
In his brief application, Qasab pleaded, "Sir, mujhe fansi ki saza Supreme Court ho gayi hai. Fansi ki saza se mujhe chorr diya jaye. Mere upar daya karo aur muje fansi ki se riha kar de. Apka Ajmal Qasab (sic)."
It was translated by the Jail Authorities as, "Sir, I have been sentenced by Supreme Court for capital punishment (Hanged till death). It is most humbly and respectfully pleaded to spare me from death sentence and also get me released from the gallows. It is my humble request. Yours"
The mercy petition was rejected by President Pranab Mukherjee on November 5, 2012.
Pakistani citizen Qasab , the sole surviving terrorist from the 26/11 terror attack, was hanged to death at the Yerawada Jail in Pune on November 21, 2012.
He was among the ten terrorists who had entered Mumbai through sea route on November 26, 2008 and launched a three-day mayhem, which killed 166 people.
25-year-old Qasab had been lodged in the Arthur Jail Road here ever since he was arrested immediately after the attack in 2008.
He was convicted and given capital punishment by the trial court on May 6, 2010, which was upheld by the Bombay High Court on February 21, 2011.
The Supreme Court subsequently upheld the sentence on August 29 last year.
Mumbai Roundup: 9 incidents that took place this week
Photos: Ajay Devgn, Parineeti, Tabu at 'Golmaal Again' trailer launch
Photos: Dipika Pallikal Karthik oozes oomph in bikinis and sarees
Photos: Kareena Kapoor Khan's grand birthday bash
Photos: 'Dangal' girls Sanya Malhotra, Fatima Sana Shaikh's dinner outing