Carson reveals details of Gwen and Blake’s vows — including song that Blake wrote

As the officiant of Blake Shelton and Gwen Stefani's wedding, Carson Daly wanted to make sure his close friends' big day was as special as possible. Part of his plan? Convincing the two musicians to write their own vows.

On TODAY Tuesday, Carson shared details from this special part of Saturday's ceremony, which took place at Shelton's Oklahoma ranch.

"I went to them months ago and said, 'I think you guys should write your own vows. We shouldn't just do the repeat after me,'" Carson recalled. "They were really reluctant to do that, but ... it's two of the best songwriters in the world, we want to hear your words."

Related: Carson, who officiated the ceremony, gave some inside scoop on TODAY.

"At the wedding, Gwen starts, and she wrote this, 'Since I was a little girl ...' And she crushes, not a dry eye in the church. ... It was so perfect," Carson continued. "I said to Blake when she was done, 'Top that, buddy.' And Blake starts by saying, 'Gwen's always giving me a hard time about not writing enough songs, so I wrote a song.'

"Guitar comes in frame, stool, next thing you know, he wrote her a song, he sings her a song while he's crying that he wrote specifically for her. ... Not a dry eye in the house."

In Carson's opinion, the song could be a major hit, but it's unclear if it will make it to an audience beyond the roughly 40 friends and family members who attended the wedding. Its working title is "Reach the Star," Blake told Carson.

"Hopefully he'll record it," Carson said. "It'll put everybody in the wedding at that moment if he records that song."

Overall, Carson said, the ceremony was "perfectly them."

"It was as elegant and refined and cool as Gwen is, and it was country and down-home and fun as Blake is," he added. "They just work. They're an unlikely pair. They're like if you paired delicious fried chicken with a glass of champagne. On paper, on the menu, it doesn't seem to work, but it works. They're comfort food with class, and everybody roots for that."

Stefani and Shelton, who met in 2014 when the former No Doubt frontwoman joined "The Voice" as a coach for its seventh season, got engaged in October of last year. For the wedding, Stefani wore two Vera Wang gowns, one long and one short, and Shelton sported blue jeans. They tied the knot in a chapel that Shelton built for the occasion on his ranch.