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More than 400 students and faculty showed support for a beloved teacher's fight against cancer by gathering outside his window to sing and worship.

The students, grades 9-12, and faculty of Christ Presbyterian Academy in Nashville, assembled outside the home of Latin and Bible teacher Ben Ellis, who's been undergoing chemotherapy treatments since he was diagnosed with cancer last year.

The group sang and played for about 30 minutes. A video from inside Ellis' home captured a moment from the powerful scene; Ellis sings along, while he and his wife look down on the crowd.

It was shared by country singer Tim McGraw on Facebook, where it's been viewed 21 million times.

Ellis wrote a message to his students, according to Good Morning America: "I love you. I believe now more than ever that God is good, and that he is with us...."

Shannon Lee Seibert commented on the Facebook post, saying that her daughter attends the school and "LOVES" Mr. Ellis, who taught her Latin for two years.

"We ALL love Mr. Ellis and his precious family. The kids were giving back to him some of the love he has given to them. He is the definition of a teacher, a role model, a servant."

Leslie Ponder also commented on the post, saying she's a teacher at the school who's "blessed to call Ben a friend."

Ponder said it was a "spur of the moment decision" to go to Ellis' house to sing.

"Students were in the middle of class..some taking quizzes and tests...and dropped everything for a bigger lesson on life, love, community, compassion. Being the hands and feet of Christ is very evident in this video...both from those looking down from the window and those looking up at the window..."

A man identifying himself as Ellis' father also made an appearance in the comments. He thanked McGraw for circulating the video.

"Thank you, Tim. Ben is my son," Bob Ellis wrote. "Through his ministry and teaching, he has positively touched countless hundreds of lives directly and many thousands indirectly. He, his wife and children are a beautiful family."

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