"One thing I know for certain is you can't keep this guy down..." the 25-year-old model wrote on her Instagram story.

Justin shared a video from the concert where he told the audience it's "so good to be here."

"This is my first day back," he declared. The Grammy winner then explained what the Justice World Tour is all about.

"As some of you guys know, the Justice Tour is about equality, it's about justice for all, no matter what you look like, no matter your shape, your size, your ethnicity. We are all the same, we're all one," he said. "We know that racism is evil and we know that division is evil, it is wrong. But we are here to be the difference makers. I want to say thank you to each and every one of you guys for being a part of this tour."

Justin also posted photos from the show, telling his fans: "Luv u guys and I missed you."

Sunday marked Justin's first performance since he was forced to postpone the remaining U.S. dates of his Justice World Tour after he was diagnosed with Ramsay Hunt syndrome, a rare virus that affects nerves in the face and ear. According to Mayo Clinic, Ramsay Hunt syndrome occurs in people who've had chickenpox and typically affects people over 60. Justin told fans he was doing facial exercises, but time is what he needed to fully recover.

Hailey, who had her own scare earlier this year when she suffered a ministroke, said the pair's health issues made them closer.

"I think honestly the silver lining in the whole situation, what I went through, what he went through, is it really bonds you. I feel like we're closer than ever," she said on Live With Kelly and Ryan. "I will take that away from everything."