A video of a cancer patient on his hospital bed singing a Christmas classic with his nurse is going viral.

Penn Pennington, now 67 is a Nashville musician who is in the Oncology ward after his cancer returned. He first was diagnosed and successfully overcame cancer a decade ago. 

Unfortunately, this time around, the cancer is more dangerous. "I've been told that it's more life-threatening, it's more aggressive, fast-growing non-Hodgkin's Lymphoma," Pennington says to Today. "Because it's so aggressive, we're having to hit it really hard," he continued. 

Throughout the treatment which includes five straight days of chemotherapy, his nurse, Alex Collazo, his nurse has become a trusted companion. 

"I wanted to do something for him to help him forget that he was in the hospital and just bring him some happiness."

“When she came into the room, she was just so bubbly and so positive about trying to make sure that I felt comfortable," the musician says. 

“I brought him my guitar and here we are now," Collazo says. 

The pair decided to sing the 1847 Christmas classic "O Holy Night" together and it has been viewed over 640,000 times. 

"We connected with our musical interest and I wanted to do something for him to help him forget that he was in the hospital and just bring him some happiness," Collazo says.