Selena Gomez and Justin Bieber has been split since 2014 but fans were recently caught by surprise when they heard their duet "Strong" released on air over at Drake's OVO Sound Radio on Oct. 17.

The song was reportedly made three years ago while they were still a couple. So why release it now? According to a source, the leak was perfectly timed to promote each artist's album.

It was reportedly no accident that "Strong" was played more than a week after Selena revealed her new album "Revival." Likewise, three weeks before Justin releases his album "Purpose" on Nov. 13. It's believed the leak was planned out for months and was made while both Selena and Justin were busy doing their own albums. A source told HollywoodLife the leak was a business strategy to help Selena and Justin with their album exposure.

"They were all well aware at the time of recording that if they did do a duet, chances are it would be picked up in some way or another. They also knew they were both going to be releasing albums in 2015, so a duet with each other would help them get more exposure if it was leaked at around the time of both of their releases. If they can piggyback off each other for more publicity, they're happy to do it," the source told Hollywood Life.

However, another source for ET Online said the duet was "never mean to be released" or leaked. The song was supposedly only made for fun when Selena and Justin were still together and trying to stay "Strong" and committed to their relationship. Fans have reportedly requested for it to be released or included in any of Justin or Selena's future albums. However, the source said that "it's not appearing on anyone's album."

The song is described by HollywoodLife as a sexy and slow track that talks about Selena and Justin's qualities. It also references their past relationship as a couple, where "The Heart Wants What It Wants" singer is heard singing about "lack of communication."  Then the duet starts where Justin, 21 and Selena, 23, sing about their love for one another.

The duet certainly had fans wishing for the couple to get back together. According to ET Online, Selena herself didn't rule out a reunion with Justin when she said that he will always be her "first love."