Hear Toby Keith's Stirring New Song 'Don't Let the Old Man In' From Clint Eastwood's 'The Mule'

'Don't Let the Old Man In' 

From 

Clint Eastwood's 

'The Mule'

Not only is Toby Keith's striking new song "Don't Let the Old Man In" featured in Clint Eastwood's upcoming film The Mule, the tune was actually inspired by a conversation Keith had with the legendary actor.

The country star said he became friends with Eastwood when they met at a California golf course. Eventually, Eastwood invited Keith to be his partner during a three-day golf tournament at the actor's Tehema Golf Club. It was then that Eastwood, who had recently turned 88, told Keith about his upcoming film project.

"I [asked] 'What keeps you going?' and he said 'I get up every day and don't let the old man in.' And I went 'I'm writing this damn thing right now'," Keith said at a recent press conference. "I didn't ask if I could put it in the movie. I just went home and wrote it and sent it to him and hoped that he would consider it. And, you know, he did."

Keith said writing a song for an American icon like Eastwood was a tall order, but it also pushed him to write the best and most powerful song he could. The song also addresses the Eastwood-inspired ethos of continuing to create and never ceasing to do what inspires you.

"I knew who I was writing it for and I knew who had inspired me to write it. I wanted to deliver him the best thing that I could," Keith said. "The second I wrote it, it was just like I jumped 500 feet in the air...I knew I had accomplished what I wanted to accomplish."

The Mule, directed by and starring Eastwood, follows a senior citizen man who becomes a drug courier for a Mexican cartel. The film will be released nationwide on Dec. 14.