The couple, who first stated dating in 2010, split last month after reuniting in June only to attend a Bible study class together, reported Daily Mirror.
"Justin looked really comfortable with Selena as he still thinks their bond is unbreakable and knows that Selena will always love him.
"The pair sat next to each other while partaking in Bible study and seemed very close. They then left together in Bieber's car," a source said.
The 'Baby' singer, 20, also fuelled speculation they are back together after briefly sharing a blurry new photograph of Gomez, 22, kissing his cheek as he holds her in his arms on his Instagram profile on August 14, with the caption, "Right now everything else is a blur."
He deleted the image seconds later.