Derek Hough Had the Best Reaction to Emma Slater and Sasha Farber's Engagement

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Emma Slater and Sasha Farber's engagement may have been the best day of their lives, but it might just be the best day of Derek Hough's life as well.

The 31-year-old Dancing With the Stars pro took to Instagram on Wednesday to share his well wishes for the happy couple, alongside an adorable gif of his reaction.

WATCH: 'DWTS' Pros Sasha Farber and Emma Slater Get Engaged in Surprise Proposal on Live TV!

"SHE SAID YES!!!! Sooooo freaking happy for @emmaslaterdanceand @sashafarber1. Love you two so much," Hough captioned the sweet clip of himself fist-pumping with joy.  "My only regret is wearing this ridiculous costume for your moment ??? #fistpump #engagement #joy #love."

WATCH: EXCLUSIVE: 'DWTS' Pros Sasha Farber and Emma Slater Dish on Epic Live Proposal: 'I Didn't Know What to Expect!'

Hough wasn't the only one excited about Slater and Farber's engagement.

ET caught up with the dancing couple just after the show -- and Farber's proposal -- where they couldn't stop gushing about the special moment.

"I was dying, I'm not gonna lie," Farber confessed. "Usually I'm like, running around and having fun backstage but I was just in the corner [before proposing]."

"I touched my hands and they were sweating, and I was like, 'Oh my god, I've still got to do this dance. And then I've got this in my pocket, what if it falls out?'" he added. "I didn't know what to expect."

"As soon as [our dance] was over, I felt his energy get even worse, like even more nervous than when we danced, and I thought that was really strange," Slater, 27, explained. "I turned to Sasha and he turned to me, and I was like, 'Ahh!' He didn't even say one word and I think I started to hyperventilate and do all that really like, ugly crying stuff, which I'm sure I'm going to regret, but it was the best day of my life!"

WATCH: EXCLUSIVE: How 'DWTS' Pros Emma Slater and Sasha Farber Celebrated Their Romantic Engagement

See more in the video below.

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