Slater and her season 23 partner, former Texas governor Rick Perry, were sent home last week, but the 27-year-old dancer was on set to perform a contemporary dance with her boyfriend as the show came back from a commercial break.
However, Slater had no idea that the whole routine was set up to give Farber the chance to pull off an amazing public proposal.
Bergeron joined the couple on stage and started with his usual show banter. "First of all, you guys have great chemistry," the host began. "And Sasha, I've always thought you had the potential to actually host. So I'm going to give the show over to you."
For a second, Slater was clearly confused, but the smile on Farber's face made things very clear, very quickly, and she was already tearing up before her boyfriend had a chance to speak.
"I've been meaning to do this for such a long time," Farber said, as he got down on one knee and pulled out a ring. "I love you so, so much."
Slater could barely contain her excitement, and as she said yes, streamers exploded from the ceiling and the crowd erupted in cheers.
Farber's friend and co-star, Derek Hough, was the first to run out on stage to hug the excited couple, and was soon joined by all their fellow dancers and contestants who came together for a giant group hug in front of a giant wall of screens that read, "She said YES!"
"Sahsa just proposed to Emma, and thankfully she said yes! Because we didn't have a graphic for the other option," Bergeron joked.
Slater later showed off the stunning ring in a pic posted to the DWTS Instagram, as her new fiance gave her a sweet kiss on the cheek.
Farber and Slater, who have been dating for over five years, moved into a cottage-style home in Los Angeles in August, and they recently invited ET along for an epic house tour. Check out the video below to see their awesome home-sweet-home.