Tanveer Ahmed, 32, from Bradford, released a lengthy statement claiming responsibility for the attack outside Asad Shah’s convenience store in the southside of Glasgow on 24 March.
Ahmed, who has been charged with murder but has issued no plea or declaration at two court appearances, said he did it because Mr Shah claimed to be a prophet and that “if I had not done this others would”.
He also denied that the incident had anything to do with Christianity or any other religion.
The statement was delivered outside court by Ahmed’s lawyer, John Rafferty.
Ahmed had also issued an instruction that it should be used in full without editing.
He has been remanded in custody and is expected to appear at the High Court at a later date.
Mr Shah belonged to the Ahmadiyya sect of Islam, a minority community which has faced persecution around the world from other Muslim groups. Ahmadis are seen as marginalised in Pakistan, where they can be targeted for their beliefs.
Several hundred of Scotland’s 77,000-strong Muslim population are believed to belong to the movement, known for their non-violent and interfaith views.
Just hours before his killing Mr Shah posted an Easter message to his customers on Facebook.
The statement released by Ahmed reads: “This all happened for one reason and no other issues and no other intentions.
“Asad Shah disrespected the messenger of Islam the Prophet Muhammad peace be upon him. Mr Shah claimed to be a Prophet.
“When 1400 years ago the Prophet of Islam Muhammad peace be upon him has clearly said that ‘I am the final messenger of Allah there is no more profits or messengers from God Allah after me.
“I am leaving you the final Quran. There is no changes. It is the final book of Allah and this is the final completion of Islam’.
“There is no more changes to it and no-one has the right to claim to be a Prophet or to change the Quran or change Islam.’
“It is mentioned in the Quran that there is no doubt in this book no-one has the right to disrespect the sayings of the Prophet Muhammad peace be upon him and no-one has the right to disrespect the Prophet of Islam Muhammad Peace be upon him.
“If I had not done this others would and there would have been more killing and violence in the world.
“I wish to make it clear that the incident was nothing at all to do with Christianity or any other religious beliefs even although I am a follower of the Prophet Muhammad peace be upon him I also love and respect Jesus Christ.”
Mr Shah, 40, was found with serious injuries after being allegedly attacked outside his shop Shah’s Newsagents and Convenience Store in Minard Road, Shawlands, Glasgow.
He was rushed to the Queen Elizabeth University Hospital where he was pronounced dead on arrival.
Hundreds of people attended a silent vigil held outside his shop, including First Minister Nicola Sturgeon.
A fundraising page has raised more than £110,000 for Mr Shah’s family, who moved to Scotland from Pakistan in the 1990s.
The Easter message that Mr Shah had posted said: “Good Friday and a very happy Easter, especially to my beloved Christian nation.”
A family statement released by police in the wake of his killing said: “On Thursday evening a beloved husband, son, brother and everyone’s friend, Asad Shah, was taken away from us by an incomprehensible act. We are devastated by this loss.
“A person’s religion, ethnicity, race, gender or socioeconomic background never mattered to Asad.
“He met everyone with the utmost kindness and respect because those are just some of the many common threads that exist across every faith in our world.
“He was a brilliant man, recognising that the differences between people are vastly outweighed by our similarities. And he didn’t just talk about this, he lived it each and every day, in his beloved community of Shawlands and his country of Scotland.
“If there was to be any consolation from this needless tragedy, it came in the form of the spontaneous and deeply moving response by the good people of Shawlands, Glasgow and beyond.”