Aaron McGuire, 28, shouted “I’m doing you” before stabbing 39-year-old father Kevin Gallacher three times.
The fatal wound was to the back of Mr Gallacher’s left thigh. He bled to death.
At the High Court in Glasgow yesterday, Lord Beckett ordered McGuire to be monitored in the community for four years after his release from jail.
He told McGuire: “You killed a man aged 39 who had been a good friend to you over many years. His partner and ten-year-old child have lost him forever. The possession of a knife transformed a minor incident into a killing.”
McGuire of Flaxmill Avenue, Craigneuk, admitted the culpable homicide of Mr Gallacher at Glencairn Avenue, Wishaw on 4 July.
The plea was accepted on the basis there had been provocation. The court heard that McGuire has previous convictions for violence.
The High Court in Glasgow heard that seconds before the stabbing Mr Gallacher had hit McGuire over the head with a beer bottle.
Prosecutor Steven Borthwick said: “In the course of July 4, both men became involved in a dispute over possession of a lawnmower.
“The precise circumstances of this dispute are unclear.
Around 11:35pm that night Mr Gallacher was standing outside 54 Glencairn Avenue when McGuire appeared.
Both men punched each other for a couple of minutes and at some point Mr Gallacher struck McGuire on the head with a beer bottle.
McGuire then stabbed Mr Gallacher, who as well as being a relative was also a friend, three times. The killer then walked to his mother’s house, covered in blood and told her “Gal kept hitting me with a Budweiser bottle”.
The following morning his mother, Maureen Cook, heard that Mr Gallacher had died and told police at the scene that her son was at her house and they should take him away.
Defence QC Tony Graham said: “This was a ridiculous dispute which escalated. He takes full responsibility for his actions. Mr Gallacher was a family member, a friend and someone for whom he had respect. He is genuinely remorseful.”
The court heard McGuire, who suffers from post-traumatic stress disorder, is “haunted” by the consequences of his actions.