"Knockin' on Heaven's Door" is a song originally by Bob Dylan.
It was featured on The X Factor by Ally Brooke and Julia Bullock in Boot Camp 2. After this performance neither of the two were picked to go to Judges Houses, with the exception of Ally, who was put into Fifth Harmony after she was eliminated.
It's getting dark too dark to see
Feels like I'm knockin' on heaven's door
Knock-knock-knockin' on heaven's door