Willie Nelson is getting some rest on doctor's orders.

The country singer, 91, canceled his appearance at the Outlaw Music Festival Tour on Friday for health reasons, a statement shared on his social media pages said.

"We regret to inform you that Willie Nelson is not feeling well and, per doctor's orders, has been advised to rest for the next four days," the statement said.

Nelson is "expected to make a quick recovery," according to the announcement.

Additional information about Nelson's health was not provided. USA TODAY has reached out to Nelson's representatives.

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Nelson was scheduled to perform Friday in Georgia as part of the Outlaw Music Festival Tour, which he is headlining. He was also set to perform on Saturday and Sunday in North Carolina.

"I am thrilled to get back on the road again with my family and friends playing the music we love for the fans we love," he said in February when the festival's lineup was unveiled.

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The announcement shared on Nelson's social media pages said the singer is expected to join the Outlaw Music Festival Tour next week, and in the meantime, his son Lukas Nelson and guests would perform a "special set" including Nelson's classics. The tour is set to move to Virginia and New York on June 26 through June 29.

This comes after Nelson was inducted into the Rock & Roll Hall of Fame last year. The "On the Road Again" singer performed with Chris Stapleton, Dave Matthews and Sheryl Crow during the induction ceremony.

"Thanks for appreciating my music," Nelson said at the time.

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In April, Nelson teamed up with Orville Peck for a duet cover of "Cowboys Are Frequently Secretly Fond of Each Other," the 1981 song about gay cowboys. In an interview with GLAAD, Peck compared Nelson's support of the LGBTQ+ community with that of Dolly Parton.

"I think that the fact that Willie stands next to the entire LGBTQIA+ community by doing this song just shows what an amazing person he is, what a legend he is," Peck said. "It's a win for all of us because that's true allyship. Someone who's completely unafraid to be right there next to us, there's no vagueness involved."

Nelson's latest album, "The Border," debuted in May.

Fans sent Nelson their well-wishes in the comments of his Instagram statement. Questlove wrote: "Godspeed Willie."

Contributing: Melissa Ruggieri and Naledi Ushe