Mr Farmer arrived at the Sydney Opera House on Tuesday morning, as part of his almost 15,000 kilometre run around Australia in support of the referendum.
"That's why I felt it was important that I dedicate six-and-a-half months of my life in actions rather than words to show the Australian people how much I cared about the future of this nation as a patriot," he told reporters in Sydney.
"And how much I cared about the future of this nation as one nation moving forward together with the First Nations people, the Indigenous people of this country."
Mr Farmer urged the nation to not "leave this to our children and our children's children to fix the problems of the past" and to seize the moment.
Meeting him in Sydney, Prime Minister Anthony Albanese said Australians should be having conversations with their families and friends to build support for the voice.
"To all those who are thinking, 'Will I spend an extra Sunday knocking on doors?' It's got to be easier than running 14,000 kilometres," he said.
A vote to enshrine the Indigenous voice in the constitution is expected to be held in October.
Independent Mackellar MP Sophie Scamps joined Mr Farmer on the run in support of the voice on Sydney's northern beaches.
"It's our opportunity to step into the future on a positive note and to show the rest of the world what type of people we are," Dr Scamps said.
"Initiatives to support our First Nations peoples to date, and to close the gap, have been a dismal failure as we have not consulted properly with the people who are affected by policies and decisions made on their behalf."
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