In the sad, lonely and overwhelming wake of the March 15 terror attack survivor only one thing was certain for Farid Ahmed - he wanted to remember his wife, and make sure others knew how important she was.

Husna Ahmed, 44, was killed as she ran back into the Al Noor mosque to find her husband, who uses a wheelchair.

Before that she had guided the women and children to safety before running back in to help others.

Several months after her death her grieving husband found some solace in writing about her life.

Pouring his heart out at his computer soon became a manuscript, and a book which is released on Tuesday.

Husna's Story - my wife, the Christchurch massacre and my journey to forgiveness follows the mother-of-one's life from birth to death.

It also contains harrowing accounts from her husband about his experience on March 15 and beyond.

The book is published by Allen & Unwin and retails at $36.00.

Ahmed is donating all royalties from all sales to St John Ambulance.

He spoke to the Herald last year about his book plans, saying he wanted to do something to pay tribute to his late wife - but also give back to the community.

He intended from the outset to donate any money from book sales to people or organisations impacted by the terror attack.

An extract of the book has been provided to the Herald.

"On the 15th March 2019, my wife and many others were victims of hate," Ahmed said.

"I wanted to do the opposite with love and forgiveness in return... I wanted to spread the message of love and peace."

He revealed he started thinking about writing three days after Husna died.

He wanted to return something to the people of Christchurch - for their love, thoughts, prayers, messages and flowers.

The idea of donating the proceeds to charity was born from his faith.

For Muslim people, acts of charity help them achieve higher status after death.

"Charity is so important in my faith because it is a token of love for mankind for it helps other's in happiness, brings peace and joy," Ahmed explained.

"I picked up St John Ambulance because they serve anyone that need help.

"I received help from them as my wife did and as many other people did.

"After the massacre, they ran to help Muslims without asking their religions or race. I love that serving spirit because I believe that mankind is one large family and we must treat each other with mercy.

"I urge everyone to help serving fellow humans by purchasing this book. I have no credit for it, it is all yours.

"I do not intend any name, fame or status for it... I just hope, it should encourage all of us that we must be sharing our love to make one another happier."

Ahmed said his love for his wife had not faded since her death.

"I love my wife and my daughter loves her mother. We had no change in it and will never change. We miss her a lot, he said.

"We both shed our tears on my daughter's birthday. I shed my tears when I visit her in the graveyard and often in other times."

He said the pain he had suffered in the last 12 months was impossible to explain.

"March 15… I can't describe the pain and agony we have been going through. It was a tragedy that shocked us terribly and changed our lives dramatically," he said.

"Life will never be the same, but life is moving on. Like the saying 'time and tide wait for none', our life journey is like waves in the ocean, they never stop moving.

He said it was important for his family - especially daughter Shifa - to focus on the positives in 2020.

The biggest thing for the pair was to accept their "fate".

"We accepted the tragedy as a part of life. Life has sadness and happiness as in 24 hours
has night and day that keeps rolling without stopping.

"Our acceptance has given us peace in mind, comfort in heart.

"We do not suffer from anger, rage, revengeful mood and have forgiven the killer."

Ahmed and his daughter had become a team with "the same vision and mission".

"The tragedy could not break our bond, could not change our loving nature," he said of their relationship.

"We chose to be positive and we found that no evil has power over us.

"We wish in the new year that there are no repeat killings, that no one weeps, no one suffers."

Farid Ahmed's book Husna's Story: My wife, the Christchurch massacre & my journey to forgiveness is published by Allen & Unwin NZ and available on Tuesday 3 March.

RRP$36.99.

All royalties to St John Ambulance.