The victory lap continued to the sacred city of Varanasi, from where he stood for parliament, ending on the banks of the Ganges which is revered by Hindus and is believed to cleanse sins.
As priests and onlookers chanted devotional songs, Modi prayed and lit a traditional oil lamp before climbing atop a flower-decked dais where he sat next to several senior BJP colleagues.
"Mother Ganges has decided my course. I will work under her guidance," Modi told the crowd while thanking local residents who elected him by a crushing margin of 370,000 votes.
Among other election promises, including ideas to build a hundred new cities and high-speed rail network, he has said he will work to clean up the filthy river whose sacred status has not prevented rampant pollution.
The controversial politician, a former tea boy tainted by anti-Muslim riots on his watch as chief minister in Gujarat, has the strongest mandate of any Indian leader in 30 years.
Modi helped the BJP to the first majority in parliament since 1984 after a campaign focused on delivering new jobs and development, despite fears raised by opponents of his impact in officially secular India.
"The country has given us an unprecedented mandate. I want to thank the country for giving us the opportunity to serve with a clear majority," he said.
In his first comments on Friday night, Modi was at pains to stress that he would work for all of India's 1.2 billion people -- including its 150 million Muslims -- to make this "India's century".
In 2002, anti-Muslim riots in Modi's home state of Gujarat shortly after he came to power as chief minister left about 1,000 dead and a lingering legacy of suspicion that he did too little to prevent the killing.
The bachelor, who has spent his career in pro-Hindu organisations, has always denied wrongdoing and investigators have found no evidence to prosecute him.
- 'Lion of Gujarat' -
"Modi is our lion! He will work for the people of India, he will work for development, he will work for every Indian," shouted Om Dutt, a 39-year-old shop owner as Modi arrived in New Delhi earlier in the day.
A crowd of supporters, who had waited at the airport since early morning while being entertained by a marching band and thumping dance music, burst through police barricades at the sight of his cavalcade arriving.
His triumph has redrawn India's political map, elevating the BJP to a pan-national force and heaping humiliation on the ruling Gandhi political dynasty, whose Congress party has been in power for 10 years.
Final figures from the Election Commission showed the BJP had secured 282 seats in the 543-member parliament, while the Congress slumped to its lowest ever tally of just 44 -- a quarter of its haul in 2009.
The defeat has raised questions about the endurance of the Gandhi political dynasty after 43-year-old scion Rahul, leading campaigning nationally for the first time, suffered a humiliating rejection.
"As long as the Congress wants them (the Gandhis) to remain as the leaders they will remain that, and the Congress party wants that," senior figure and outgoing minister Kamal Nath told CNN-IBN television Saturday.
- Goodbye to Singh -
Beleaguered outgoing Prime Minster Manmohan Singh resigned on Saturday, ending his 10 years in charge, and a final televised address thanked the Indian people for their support."Today India is a far stronger country than it was a decade ago," the 81-year-old said in a typically low-key speech -- a great contrast to the bombastic, high-energy style of his successor.
Modi is expected to be sworn in next week, and Singh will remain in office on a caretaker basis until then.
In national capitals across the world, leaders readjusted to the change in leadership, with the US and Europe having to quickly embrace a man who has been shunned for a decade.
Modi was boycotted by many Western countries over the 2002 riots.
The United States, Britain and Australia were quick to extend invitations for him to visit, while Prime Minister Nawaz Sharif from neighbouring Pakistan rang to offer congratulations on an "impressive victory".