Justin Bieber posted a picture of himself with Selena Gomez on Friday, July 5, a day after a source confirms the two spend the July 4 holiday together. Credit: Courtesy of Justin Bieber

Are Justin Bieber and Selena Gomez back on? A day after a source tells Us Weekly exclusively that the former lovers were at a 4th of July party together, the "Beauty & The Beat" singer posted a picture of the pair on his Instagram page on July 5.

It's unclear when the photo is from, but Bieber, wearing sunglasses and a backwards hat, is alongside Gomez, 20, who wears a black hoodie, sunglasses and bright red lipstick. The 19-year-old singer captioned the picture "#Heartbreaker," which happens to be the title of his upcoming new single. On July 3, he posted the art for the new single -- an image of cupid shooting an arrow at a purple heart made of dust -- and wrote "it's gonna happen suddenly."

An insider confirms to Us that the on-and-off-again couple -- who dated for two years before splitting last fall -- were "in a great mood" while celebrating the 4th together. "They arrived holding hands," the source reveals. "Justin was in a good mood."

Indeed, Bieber tweeted after the Independence Day celebrations: "Great night." (On her own Twitter page, Gomez wrote, "Happy Birthday America!!! Hope everyone is enjoying the day." She later posted a picture of herself with six girlfriends, including actress Francia Rasia).

While talking to Us Weekly exclusively for its new bookazine, the Canadian native revealed that it is possible to be friends with an ex. "As long as people are kind to each other during a breakup, there is no reason they can't be friends," he shared.

"My grandparents [Bruce and Diane Dale] are my relationship role models," he added, "They love each other so much, after so many years! When I'm their age, I want to be as in love with my wife as my grandfather is with his."

Tell Us: Are you surprised the pair spent July 4th together?