Kelly Clarkson and Ariana Grande Look Back at Their 2013 Twitter Exchange and Preview Christmas Duet

Before coaching together on 'The Voice,' these two were big fans of each other!

Kelly Clarkson and Ariana Grande are having the best time coaching together on The Voice!

Despite the contentious nature of the show's Blind Auditions (and Blake Shelton's best efforts at pitting them against each other), the powerful vocalists couldn't be bigger fans of each other, with Kelly remarking on Tuesday's show how she loves "having female energy back in the mix" of the singing competition.

In fact, Kelly and Ariana have admired each other for nearly a decade. On Thursday, Kelly shared a screenshot of the now-infamous tweet she sent upon seeing Ariana and Mac Miller performing their hit, "The Way," on The Ellen DeGeneres Show way back in 2013.

"Okay, who the heck is this girl & where did she come from?!" Kelly's tweet reads. "Someone just sent me this & wow she is killer & only 19!"

Ari even replied to the tweet at the time, writing, "omg that's me hi kelly clarkson thank you ily."

Kelly shared the screenshot alongside a cute pic of her and Ariana on The Voice set, writing "How it Started vs. How it's Going ❤️ Y'all, I love this girl! Did I mention she's gonna be on my upcoming Christmas album!?"

Ariana shared the post on her Instagram Story, writing, "this post? @kellyclarkson YOU ARE...... CUTE.... beyond honored to sing with you. I love this record and you."

The pair will be teaming up for a duet, "Santa Can't You Hear Me" on Kelly's upcoming Christmas album, When Christmas Comes Around, but they already got to perform together during The Voice's season 21 premiere last week. Kelly and Ari teamed up for a soaring duet of Aretha Franklin's "Respect," which then mashed up with Blake and John Legend's performance of Sam & Dave's "Hold On, I'm Coming."

"What an honor to perform with them!" Ariana said ahead of her Voice debut moment.

The Voice airs Mondays and Tuesdays at 8 p.m. PT/ET on NBC. See more from season 21 in the video below!