The prime minister said that the phrase which prompted a worldwide viral trend said "more than he ever could" about Saturday's knife attack, which left a 56-year-old with serious injuries.
Speaking in the Midlands, Cameron said: "Some of us have dedicated speeches, media appearances and sound bites, and everything to this subject but 'You ain't no Muslim, bruv' says it all much better than I ever could.
"Thank you because that will be applauded across the country."
Perhaps predictably, people online were quick to respond to Cameron's use of the phrase.
David Cameron just said '#YouAintNoMuslimBruv'. I reckon he only approves because like his policies it's double negative.— Tiernan Douieb (@TiernanDouieb) December 7, 2015
David Cameron says whoever shouted #YouAintNoMuslimBruv said it better than he ever could. That's cos he'd sound like a tit if he'd said it.— Neil Humphreys (@NeilHumphreys) December 7, 2015
David Cameron saying #YouAintNoMuslimBruv in a speech is like your Dad dropping 'Major Lazer's latest jam' into a conversation.— Anisa Subedar (@OnlyAnisa) December 7, 2015
David Cameron just said: "You ain't no Muslim, bruv" and here's the proof https://t.co/35dbWeniFs— Elliot Wagland (@elliotwagland) December 7, 2015
WELL YOU'VE RUINED IT NOW DAVID CAMERON I HOPE YOU ARE HAPPY https://t.co/TxcjMNrqxn— Elena Cresci (@elenacresci) December 7, 2015
Video apparently filmed as police moved in to make the arrest shows commuters lambasting the assailant, with at least one man shouting: "You ain’t no Muslim bruv! You ain’t no Muslim!"
While it is still unclear who captured the footage and who made the remark, the phrase quickly trended on social media.
The Met Police has said it is investigating the attack as a "terrorist incident."
The Met's head of Counter Terrorism Command, Commander Richard Walton, said: "I would urge the public to remain calm, but alert and vigilant. The threat from terrorism remains at severe, which means that a terrorist attack is highly likely."
Cameron delivered the line during a speech in Burton-on-Trent promoting government achievements, including policy to build hundreds of thousands of new homes.
He announced a number of new policy initiatives including allowing people who part-own, part-rent properties through shared ownership schemes to "trade up", providing £8m for councils to prepare land for starter homes, and new targets for the number of apprentices in the public sector.