John Lennon's son Julian Lennon on Saturday broke his wow and performed Imagine for the first time in public. (Image via Stephane Cardinale/Getty)Julian Lennon, legendary singer John Lennon’s son, broke his vow to never sing his father’s song Imagine by performing it for the first time publicly at the Stand Up for Ukraine event. Julian mentioned that he believed he would only sing the track if it was the end of the world. Calling it "an unimaginable tragedy," he tweeted:"As a human, and as an artist, I felt compelled to respond in the most significant way I could. So today, for the first time ever, I publicly performed my Dad’s song, IMAGINE."Speaking about breaking his vow to never sing the song, Julian Lennon wrote in a Twitter thread:“Why now, after all these years? - I had always said, that the only time I would ever consider singing ‘IMAGINE' would be if it was the ‘End of the World'. Because within this song, we’re transported to a space, where love and togetherness become our reality, if but for a moment in time. The song reflects the light at the end of the tunnel, that we are all hoping for."Julian Lennon@JulianLennonThe song reflects the light at the end of the tunnel, that we are all hoping for...As a result of the ongoing murderous violence, millions of innocent families, have been forced to leave the comfort of their homes, to seek asylum elsewhere.9:33 PM · Apr 8, 20221293174The song reflects the light at the end of the tunnel, that we are all hoping for...As a result of the ongoing murderous violence, millions of innocent families, have been forced to leave the comfort of their homes, to seek asylum elsewhere.Fans and artists react to Julian Lennon’s performance of ImagineAfter Julian Lennon's performance of Imagine, fans took to Twitter and praised him for taking a prominent step for peace.Tatyana Bartusevych@official8191 Julian Lennon broke his old vow and for the first time performed the most famous solo song of his father - the founder of The Beatles John Lennon. And all because of the war in Ukraine.1:25 PM · Apr 10, 2022107862959❤️ Julian Lennon broke his old vow and for the first time performed the most famous solo song of his father - the founder of The Beatles John Lennon. And all because of the war in Ukraine. https://t.co/Jzb1XU3xLBSeth Abramson@SethAbramsonIf a celebrity was ever going to sing “Imagine” for a good cause, this was the way to do it: Julian Lennon, singing his father’s song for the first time ever—for Ukraine. Julian and John had a fraught relationship, which is why he’s never sung this before. youtube.com/watch?v=NicWjY…04:18 AM · Apr 11, 20222698684If a celebrity was ever going to sing “Imagine” for a good cause, this was the way to do it: Julian Lennon, singing his father’s song for the first time ever—for Ukraine. Julian and John had a fraught relationship, which is why he’s never sung this before. youtube.com/watch?v=NicWjY…Greg Peck@gregoripekoe"I've always said that the only time I'll ever perform "imagine" is the end of the world". Julian Lennon4:52 PM · Apr 10, 202216743"I've always said that the only time I'll ever perform "imagine" is the end of the world". Julian Lennon https://t.co/pVXFSKuPupJane of the North@TrulyNorthernThank you Julian Lennon. This is beautiful.06:18 AM · Apr 11, 202221153Thank you Julian Lennon. This is beautiful. https://t.co/ld5AakcgFeBillie Eilish also performed at the Stand Up for Ukraine eventbillie eilish@billieeilishWatch Billie's performance of "Your Power" live and join @GlblCtzn in the #StandUpForUkraine rally for refugee relief. ForUkraine.com youtu.be/jsQnCFyIoUk11:01 PM · Apr 9, 20228341963Watch Billie's performance of "Your Power" live and join @GlblCtzn in the #StandUpForUkraine rally for refugee relief. ForUkraine.com youtu.be/jsQnCFyIoUkGrammy-award winner Billie Eilish also performed her song Your Power at the event and said that her performance was in honor of the people of Ukraine. Other performers at the event included U2, Chris Rock, Demi Lovato, Jonas Brothers, Katy Perry, Green Day, Hugh Jackman, among others. The artists urged world leaders to help the people who have been displaced in the backdrop of the Russia-Ukraine crisis.Billie Eilish performing at the Concert for Ukraine. (Image via Youtube)The 'Stand Up For Ukraine' event took place this Saturday and was convened by European Commission President Ursula von der Leyen and Canadian Prime Minister Justin Trudeau in partnership with Global Citizen. The event saw $4.6 billion in grants and $5.5 billion in loans pledged for humanitarian efforts being undertaken by Ukraine and other European countries, UN agencies, and grassroots organizations to support Ukrainians and refugees.